I have just switched to O2 yesterday. Once my previous sim stopped working, I fired up my new sim and can send texts and make phonecalls but cannot receive texts or calls. The network coverage says a mast may not be working as it should in my area but nobody else I know on O2 is having any issues.
We’re just customers like you but it sounds like you’ll need someone to access your account which can’t be done from here. If you message O2 on Facebook (https://o2uk.co/O2CFB) , Twitter (https://o2uk.co/O2CTW) or Instagram (https://o2uk.co/O2CIG) , they should be able to help you with this111
It can take up to 24 hours for everything to fully port over.
Keep rebooting your phone as it helps complete everything.