Is there anything i can do about stolen phone

[YorkshirePuddingsS]

My son lost his phone, he didnt have a password on it, absolutely stupid i know, someone has found it and is using it. Is there anything i can do as i think my bank details might be on there, uber eats etc apple pay maybe? Anything i can do at all?

When an IMEI is blocked by any network, it is blocked across all networks, not just the one issuing the block.

Update: We found out that he does have find my iPhone enabled, I’m not good with tech but found out he does have it on so does anyone know are we better off reporting it as lost, or erasing the iPhone? Will erasing it delete his iCloud pics? He thinks we shouldn’t mark it as lost as he reckons the person has probably put a passcode on now so that wouldn’t work so should we erase it? Will he lose his iCloud data? The tracking shows it in Manchester, we are in London 🙄

Do both. The new user having a passcode on doesn't affect the ability of the networks to bar the IMEI.
Your son will keep all of his backed up data, because wiping it wipes the phone and not the cloud back up.

Ok thank you so much! We are relieved to have realised he did have it on so we know exactly where it is now just miles away in Manchester!