Anyone else received spam calls from another operator? Claiming to be associated with O2 and offering to reduce the bill. Cheeky sods.
I guess the main question to 02 is - how did they get my number and know that I'm on 02? (And no, I don't put my number on random internet sites)
You can also block the number and report it free to 7726.
O2 advice here:
How to block a number:
Scammers can look up the number ranges to determine which network they originated from and then hope the number hasn't been ported out to a different network.
In short, they don't necessarily know which network you are on now, just what network the number was originally associated with.