You need to resend your form again. https://www.o2.co.uk/help/phones-sims-and-devices/how-to-keep-your-mobile-number
It wont happen over the weekend.
Numbers here Guide: Coronavirus Community Help and Support
Advice from an O2 Guru regarding a way to get through:
If you call 202, when it comes to the reason you are calling stay silent for 15 seconds and you will be taken to the keypad options.
Press 2 for Everything Else
Press 5 for More Options
Press 7 for Anything Else which will put you though to an advisor.
Press Upgrade, Lost/Stolen if you have to.
Edited for info
Veritas Numquam Perit
Settings >Phone >My Number
Change it to your phone numberm save and reboot phone.