The UK’s business mobile network

A phone system built into the network.

Landline and mobile numbers on one SIM, every call and text recorded, hunt groups and IVRs - on the phones your team already carries. No apps, no VoIP.

Get started Request a quote

Or talk to us: 0333 880 4008 · WhatsApp

Trustpilot
8,500+ UK businesses on the network
Since 2013 putting landlines on SIMs
To your office line · 0161 496 0123
07700 900461
Incoming call
Also on this SIM: mobile 07700 900812

Your landline and mobile on one SIM

Businesses on ONSIM
8,500+
Calls a month
4.53m
Landline SIMs since
2013
Network monitoring
24/7

Built for the way your team works

If your business runs on mobiles, you already know the problems.

  • Missed calls
  • Personal numbers on business cards
  • VoIP apps that drop out
  • Recordings that never happened
  • Customers who can’t reach the right person

On the road

Drivers reachable on one company number, with every call logged - including the ones nobody answered.

Couriers → Taxi firms →

See every sector we work with →

Only on ONSIM

What your current network can’t do

Mobile networks have offered the same service for decades. Because ONSIM is the network, we can build in the things businesses ask for - the ones other carriers will tell you are impossible.

Your landline, your mobile, or both

Other networks
Other networks: One SIM, one 07 number. Want a landline too? That means a VoIP app or call diverts.
ONSIM
ONSIM: Your mobile number, your 01, 02, 03 or 08 landline, or several of each - all on one SIM, all ringing your phone. No app, no diverts.
Landline SIM →

Choose the number customers see

Other networks
Other networks: Customers see whichever number the SIM came with, every time.
ONSIM
ONSIM: Each user picks which of their numbers to show - landline (01, 02, 03, 08) or mobile (07) - and can change it any time in the dashboard.
Caller ID → Try it

Recording that can’t be bypassed

Other networks
Other networks: Recording apps and diverts that miss calls, or get switched off.
ONSIM
ONSIM: Calls and texts recorded inside the network. Nothing on the handset for anyone to turn off.
Call & SMS recording → Try it

SMS Intercept

Other networks
Other networks: Texts go straight to the recipient. You find out what was sent afterwards.
ONSIM
ONSIM: Put your firm in the SMS path, so texts can be checked and validated before they’re sent.
SMS recording & Intercept →

Attempted calls, logged

Other networks
Other networks: Calls that ring out unanswered leave no trace at all.
ONSIM
ONSIM: Every call attempt logged in real time, in your dashboard and over our API.
Why other networks don’t →

AI built into the network

Other networks
Other networks: Reroute your calls through a VoIP platform to get AI on them.
ONSIM
ONSIM: Every recorded call transcribed and searchable in plain English - on an ordinary mobile.
AI Insights → Try it

Other networks give you a SIM

We give you the phone system too

Welcome messages, menus, hunt groups, queues - everything an office phone system does, run by the network itself on the mobiles your team already carries. No switchboard, no desk phones, no VoIP app.

One call, start to finish
  1. A customer calls 0161 496 0123
  2. Welcome message
    “Thanks for calling Brightwell Lettings.”
  3. Menu
    1 Lettings 2 Maintenance 3 Accounts
  4. Lettings hunt group rings every mobile
    James Emma Ravi
  5. Emma answers on her mobile
    When she calls back, the customer sees the same office number.
Welcome messages Callers hear your greeting before anything rings - recorded, uploaded or generated from text. IVR menus “Press 1 for sales, 2 for support” - answered in the network, put through to mobiles. AI receptionist An AI that speaks with your callers, configured for your business. Hunt groups One number rings several mobiles, all at once or in order. One included with 2+ Landline SIM users. One number, whole team Share a main number across multiple SIMs, for calls in and out - every caller sees the same number. Call queues Callers hold with music and keep their place in line, answered in order by staff on mobiles. Timed routing & failover Different rules for office hours, evenings and holidays - unanswered calls passed on automatically. Music on hold Played by the network. Upload it once and every hold, queue and transfer uses it. Voicemail to email Every voicemail delivered to your inbox as an attachment. Call screening Known callers straight in, nuisances turned away - decided before your mobile rings. Conference calling Dial-in conference rooms on your business number, plus three-way calling from any ONSIM mobile.

Tell us how your calls should flow and we’ll set it up with you. Then manage it from one dashboard, and read your users, hunt groups and IVRs back over our API. Try the call flow builder →

Integrations

Your calls and texts, in the systems you already use

A recording is only useful if it’s where your team and your regulator expect to find it. Calls and texts are captured by the network in exactly the same way, and ONSIM gets them - with transcripts and call logs - into your CRM, your compliance archive or your own cloud storage.

Captured by the network

Calls and SMS on your recording-enabled SIMs and numbers - no app on the phone, no gaps.

Recorded the same way
A call
  • recording.wav
  • transcript.json
  • metadata.json
A text
  • message.json

Who sent it, who to, when, and the full message.

Into
  • Your CRM
  • Smarsh
  • ASC
  • SteelEye
  • AWS S3
  • Your data warehouse
New

Customer API

Pull your calls - every leg, who answered, what was missed - and their recordings into your own systems. Read your users, numbers, hunt groups and IVRs too. Read-only, so it never changes your account.

Read the API docs →

SFTP feed

Every call delivered as a set: the audio, a JSON file of call metadata and, with AI Insights, the transcript - ready for your archive or compliance platform to pick up.

Transcription schema (PDF) →

Straight to your storage

Call recordings and text messages delivered directly into your own AWS S3 storage, so they sit under your retention policy alongside everything else you keep.

Get a quote →

Don’t take our word for it. Try it.

These are live demos of the ONSIM dashboard, running on sample data.

Call from your landline number on your mobile

Each user chooses the number customers see: your office landline, an 03 number or their mobile. Your personal number stays private.

Business landline on mobile →
app.onsim.uk › Team › James Okafor › Profile
Sample data
Phone number(s)
Choose which number people see when James calls them.
Landline
0161 496 0123
Mobile
07700 900812
Incoming call
0161 496 0123
Manchester
Decline
Accept

What your customer sees

What customers say about our team

The network is the clever bit. The people are why customers stay.

Amazing company the service is second to none! Support staff are great and have helped me so much. Really polite and helpful.
SS Smith & Sullivan Ltd Small business owner
ONSIM have been utterly brilliant with their customer support. Thoroughly professional and fully committed to supporting their customers.
S Scott Small business owner
I have two businesses and the staff at ONSIM were brilliant.....instant replies and very polite couldn’t ask for more from them. Thanks for everything
JM John Morrison Small business owner
Great for businesses wanting to give a ‘local’ impression without costly landline contracts. They are saving us ££s every month!
OC ONSIM customer Small business

Read more reviews on Trustpilot →

The ONSIM team

Who you’re dealing with

A real network, run by real people

We’ve been putting landline numbers on mobile SIMs since 2013. We put customers first, we listen to feedback from businesses of every size, and if something isn’t right we want to hear about it.

  • Call or WhatsApp us
    0333 880 4008 Start a WhatsApp chat
    Mon–Fri, 9am–5pm UK time
  • Email us
    support@onsim.uk
    Picked up next working day out of hours
  • Our offices
    London (registered office) and Ballasalla, Isle of Man
  • Always watched
    Our network is monitored 24/7 for outages and security threats
Member of the Communications Ombudsman scheme Cyber Essentials certified All contact details →

Businesses that switched

QLine IT Live in days
QLine IT sees every customer call - recorded, transcribed and dashboarded
Team on ONSIM: ~15 people
Recruitment Live in under a week
A 250-agent medical recruitment agency closed its call recording gap in under a week
Agents on ONSIM: 250
Banking Live in 48 hours
A multinational bank replaced clunky mobile recording across regions in 48 hours
Compliance coverage: Gap closed
All customer stories →

Switching is simple

  1. 1

    Tell us what you need

    Sign up online, or call us and talk it through. We’ll help you pick the right SIMs, numbers and recording set-up.

  2. 2

    Bring your numbers

    Port your existing landline and mobile numbers in, just like any other network. Install eSIMs from a QR code or use physical SIMs.

  3. 3

    Run it from one place

    Manage users, numbers, call flows and recordings from your dashboard, and pull your calls and recordings into your own systems over our API.

FAQs

Frequently Asked Questions

With all revolutionary technology there will always be lots of questions. The section below covers the most frequently asked, but please contact us if there is anything else you would like to know.

Why ONSIM?

Mobile networks don't innovate. They've offered the exact same service since the 70's and whilst the phones we use have changed dramatically, the networks they rely on have not kept up. We're on a mission to disrupt the mobile industry and improve it for all.

Do I need to change SIM?

Yes, all our unique features only work when you use our SIM's & network. You can port your existing mobile and landline numbers as you would to any other telecoms provider.

What is the coverage like?

In the UK our network covers more than 99% of the UK population and 90% of the landmass and it's powered by the UK's leading network, winner of the overall performance category for RootMetrics' tests 9 years running. We also have WiFi Calling for low coverage areas. When our users travel to other countries we will sometimes change the network to give access to local services and remove roaming restrictions/charges.

Can I use my existing number?

Yes - you can port (or transfer) your existing landline or mobile number to use on the ONSIM service just like any other mobile network or telecom service provider.

What number will be displayed when I make a call?

It's your choice. Unlike other mobile networks ONSIM customers can display either a landline (01,02,03,08) or a mobile (07) number to the person they are calling. This is especially useful for hiding your personal mobile for work.

Do I need to install any apps?

No - our service is SIM based it doesn't even have to be a 'smart' phone. This makes it more reliable and the call quality is far better than using a VoIP App.

Discover more content in our Blog

View all posts »

The ONSIM blog is our narrative on the mobile industry, mobile tech and points of interest for our wide array of customers. We hope you find it useful and informative.

ONSIM Launch the Customer API (V1)

ONSIM Launch the Customer API (V1)

Our read-only Customer API is live. Pull your calls, every leg and outcome, recordings, users, numbers, hunt groups and IVRs straight from the network into your own systems.

Ask your network for the impossible

Bring your existing landline and mobile numbers - we port them just like any other network. Then do the things they couldn’t.

Get started Get a quote

Or call 0333 880 4008 · chat with us on WhatsApp