There is a requirement by Ofcom for O2 to prevent calls from numbers that have been identified as having invalid or incomplete Calling Line Identification (CLI) data. These numbers will be blocked or stopped by either the originating provider or receiving provider.

There are a few ways in which a number would fall into this category. Ofcom regularly gives us a list of numbers which we have to block or stop as part of our regulatory responsibilities. There are also unallocated number ranges which should not be used by anyone, as they’re not available for use. Like numbers starting 05 or 06.

Occasionally a number may be accidentally blocked or stopped. If you think this has happened to you, get in touch.  

We’ll investigate why the number has been blocked or stopped, and will look to fix the problem as quickly as possible.  

If you’re an O2 customer and receiving nuisance calls, read our advice on unwanted calls and texts to find out how to stop them. We’re unable to block calls on your behalf, but you can check your phone guide to find out how to block them yourself.