Virtual Landline vs Landline SIM: Which Do You Need?

If you have been searching for a way to get a UK landline number without a physical line, you have probably come across two terms: virtual landline and Landline SIM. Both let you use a proper 01, 02 or 03 number. Neither requires an engineer visit or a broadband connection. But they are not the same product, and picking the wrong one will leave you with a setup that does not quite fit how your business works.

This guide explains the practical difference between the two, what each one is genuinely good at, and the questions worth asking before you decide.

What is a virtual landline?

A virtual landline is a UK business phone number that is not tied to a physical location. Instead of routing calls down a copper telephone line to a fixed handset on your desk, the number lives in the cloud and delivers incoming calls to wherever you specify: your existing mobile, a landline, a VoIP app, or a combination of all three.

Most people searching for a virtual landline are looking for something simple: a professional-sounding 01 or 02 number that rings on their mobile, without the cost of a traditional phone line. A virtual landline from ONSIM does exactly that, starting from £5 per month.

The technology behind a standard virtual landline is call forwarding. When someone calls your business number, the call is routed to your mobile via the public network. To the caller, it looks like a normal landline call. On your end, it rings exactly like any other incoming call on your mobile.

What virtual landlines are great at:

• Giving sole traders and startups a professional number quickly and cheaply
• Letting a small team share a single business number
• Adding a local area code when your business operates in a specific region
• Receiving business calls on a personal mobile without mixing numbers

What standard virtual landlines cannot do:

• Show your landline number when you call someone (outbound calls display your 07 mobile number)
• Record calls at the network level for compliance purposes
• Work independently of your existing mobile contract
• Handle the volume and reliability that a growing team needs

What is a Landline SIM?

A Landline SIM is a physical SIM card (or eSIM) that gives your mobile a landline number as its primary identity on the network. Rather than forwarding calls to your phone, the calls are delivered natively to the SIM itself, over the mobile voice network, the same way a normal mobile call works.

The practical difference is significant. When you use a Landline SIM, your phone’s built-in dialler and contacts work with a 01 or 02 number the same way they would with a standard 07 number. There is no app to keep open, no internet connection required for calls, and no forwarding chain adding latency or failure points.

When you call someone from a Landline SIM, your landline number appears on their screen. Not your mobile number. Not a withheld number. Your actual business landline. This is the single most common reason businesses upgrade from a standard virtual landline to a Landline SIM: outbound caller ID.

Using a Landline SIM with dual SIM

One of the most practical ways to use a Landline SIM is alongside your existing personal SIM in the same device. Most modern smartphones support dual SIM, either through two physical SIM slots or one physical slot plus an eSIM. ONSIM supports both formats, so you can add the Landline SIM as a second profile on a phone you already own without removing your personal SIM.

The result is a clean separation of business and personal on a single device. When a business call comes in, it rings on your landline number. When you call a client, you select the ONSIM SIM from your dialler and your 01 or 02 number is displayed. Personal calls carry on as normal from your personal SIM. No second handset, no app switching, no call forwarding delays.

For businesses with a BYOD policy this is particularly useful. Staff keep their existing personal number and contract, and the ONSIM eSIM is added as a business profile on top. The company has full visibility of business calls through the ONSIM dashboard while personal calls remain completely separate. When someone leaves, the business SIM profile is simply removed, with no need to recover a handset or port a number.

What Landline SIMs are great at:

• Full two-way calling with your landline number displayed on outbound calls
• Teams that want a single business number ringing across multiple mobiles without a traditional phone system
• Clean separation of business and personal calls on one device using dual SIM or eSIM
• Businesses that need calls to work reliably regardless of Wi-Fi or broadband
• Mobile workers, tradespeople, field teams and anyone who is rarely at a desk
• Companies preparing for the PSTN switch-off who want a future-proof setup
• Businesses in regulated sectors that need network-level mobile call recording
• International use: ONSIM Landline SIMs roam like at home in 39 countries

Side-by-side comparison

Which one is right for your business?

Choose a virtual landline if:

You are a sole trader or a very small business that mainly needs to receive calls looking professional. If most of your calls come in rather than go out, and you are happy for outbound calls to show your mobile number, a virtual landline is the simpler and cheaper option. It takes minutes to set up and works immediately with your existing phone and contract.

A virtual landline also makes sense if you want to test having a separate business number before committing to a different SIM or contract.

Choose a Landline SIM if:

You make as many outbound calls as you receive, and you want customers to see a proper business number rather than a 07 mobile. This is the point where most businesses find a virtual landline insufficient, because winning new customers over the phone is harder when you are calling from what looks like a personal mobile.

A Landline SIM is also the better choice if you have more than one or two people who all need their own business number, if your business needs to operate across the EU and USA without roaming charges, or if you are in a sector where call recording is a compliance requirement.

Because the Landline SIM operates on the mobile network rather than using forwarding or internet delivery, it is also more reliable in poor signal areas and requires nothing more than your standard phone dialler to use.

How ONSIM approaches both

ONSIM has been providing SIM-native landline services since 2013, which means the Landline SIM is very much the core product. The virtual landline offering exists because some customers genuinely want the simpler entry-level product, and it makes sense as a starting point.

The natural progression for most ONSIM customers is to start with a virtual landline and then switch to a Landline SIM once outbound caller ID becomes a priority, usually when they start proactively calling leads or clients rather than just taking inbound enquiries.

Unlike the generic “virtual landline” services that are essentially number forwarding businesses, ONSIM operates its own mobile network. That means features like network-level call recording, IVR, hunt groups, and real-time account management are available without relying on third-party apps or over-the-top software.

Frequently asked questions

Is a virtual landline the same as a Landline SIM?

No. A virtual landline forwards incoming calls to your existing mobile number. A Landline SIM replaces your SIM so that the landline number is the native identity of the device itself. The Landline SIM handles both inbound and outbound calls natively without forwarding.

Can I show my landline number when I call someone?

Only with a Landline SIM. Standard virtual landlines forward incoming calls to your mobile, but when you call out, your 07 mobile number is displayed. With a Landline SIM, your 01, 02 or 03 number is shown on outbound calls.

Do I need to change my phone to use either service?

A virtual landline works with your existing mobile and SIM. You do not change anything. A Landline SIM requires swapping your current SIM for an ONSIM one, or installing an ONSIM eSIM as a second profile if your phone supports dual SIM. Your existing mobile number can be ported to ONSIM so you keep it.

Will either work without Wi-Fi?

Both will. The virtual landline uses the standard mobile voice network to deliver the forwarded call. The Landline SIM also uses the mobile voice network natively. Neither relies on Wi-Fi or a broadband connection to make or receive calls.

What happens to my landline number during the PSTN switch-off?

If you currently have a traditional 01 or 02 number on a copper phone line, that line will stop working when BT switches off the PSTN network. Both ONSIM products use mobile or cloud delivery and are completely unaffected by the switch-off. Your number can be ported across so it keeps working after the deadline.

How much does each cost?

ONSIM’s virtual landline starts at £5 per month plus VAT for a single inbound number. The Landline SIM starts at £10 per month plus VAT, which includes unlimited UK calls and SMS and the ability to make outbound calls displaying your landline number. Full pricing is on each product page.

If you are still unsure which fits your situation, the simplest test is this: do you regularly call customers and want them to see a professional number? If yes, the Landline SIM is the right choice. If you mostly receive calls and want a professional number to give out, a virtual landline will do the job at a lower cost.

Either way, both products are available with no engineer visit, no broadband requirement, and no lengthy contracts. You can sign up for a virtual landline or get a Landline SIM and be up and running the same day.