So I transferred over my O2 number to EE on Monday after ordering a new phone last week, and for some reason beyond me I cannot receive verification emails from any of my banks or from Microsoft (banks being NatWest, First Direct and Santander) - there might be more companies, I don't know, but these are the only ones I've needed to verify so far.
I've been in contact with EE over the phone who had removed some 'security barriers' and I was told to reset my phone afterwards - no change, unsurprisingly. I then got in contact with them again and explained this, for me to receive a response saying it's something on the bank's behalf as to why this keeps happening, however when I mentioned that it was also the same result when verifying my Microsoft account, they didn't have much blaming to do after that! But nonetheless, nothing was resolved - I wasn't even given a 'next steps' solution, so as you can imagine I'm starting to lose hope.
If anyone has any advice or knows of anything else I can do, please reach out - I'm still within my 14 day cooling off period so time is pretty sacred before I contemplate cancelling this altogether.