Call screening - your number, your door policy
A published business number attracts everyone: customers, suppliers, and an endless procession of diallers, "have you been in an accident" scripts and silent calls. Call screening puts a door policy on the number - known callers straight in, unknowns triaged, nuisances turned away - all decided in the network before your mobile ever rings.
Screening rules that run in the network
Phone-based "spam blocking" apps work on the handset, after the ring has already interrupted you, and only on that one device. ONSIM screening runs where the call arrives - in the network - so a rejected caller never rings any of your phones, and the same rules protect every user on the account. Reject withheld numbers, allow-list your key customers so they always get through, deny-list repeat offenders, and send everyone else via the route you choose: a receptionist menu, a hunt group, or straight to voicemail-to-email.
Rules are self-served in the dashboard and pair naturally with timed call routing - screen harder out of hours, softer during the working day.
Call screening questions
What is call screening?
Deciding what happens to a call BEFORE your phone rings, based on who is calling. Screening ranges from the blunt (reject all withheld numbers) to the surgical (this customer always rings straight through, unknown numbers go via a menu, that persistent cold-caller goes nowhere). On ONSIM these rules run in the network, so they work identically on ordinary mobiles with no app.
Can I block anonymous and withheld numbers?
Yes - anonymous call reject is a standard control. Callers who withhold their number can be refused outright or diverted to voicemail, which alone removes a large slice of nuisance calls to business numbers. Legitimate callers who withhold by default (some public bodies do) can be handled with a specific rule instead of a blanket one.
What happens to calls I screen out?
Your choice per rule: reject, send to voicemail-to-email so you still get a message as a recording in your inbox, or route through your virtual receptionist so genuine callers can still reach the right person while diallers give up. Screening does not have to mean losing calls - it means triaging them.
How do I know which numbers to screen?
Our free phone number checker shows what is known about any UK number that has been calling you - including community scam and nuisance reports from thousands of users. Check the number, then set the rule.
Is call screening included?
The screening controls (anonymous call reject, selective acceptance and rejection, caller identity rules) are part of the ONSIM platform on Landline SIM accounts, managed in the dashboard. No extra hardware, no app, and rules take effect immediately.
Getting nuisance calls right now?
Look the number up first in the free UK phone number checker - it shows who the number belongs to and what other people have reported about it. Then put your door policy in place.