Can't pay O2 iPad bill, it tries to send text but I can't receive it

[Neonpossum]

Hey all, I have an iPad Pro 12.9" and I usually sign into O2 to pay the bill. This time, it asks me to input a code and states it's sent a message to the SIM's phone number that is associated with the iPad. I obviously cannot receive texts on the iPad and moved the SIM to my phone (Galaxy S21), but still could not receive any messages. When looking at the SIM in settings, it says 'number unknown' in both the iPad and the phone. 

I have no idea how to get around this, all I wanna do is pay my bill 😞 Help?

[MI5 · Accepted solution]

@Neonpossum 

This is a new security feature that O2 will not waiver.

I suggest you set up a direct debit to avoid future problems.

You can reach the Payment Management team on 0800 902 0217.
The opening times are:
Monday to Friday – 8am to 8pm
Saturday – 8am to 6pm
Sunday – 9am to 6pm