App frustration

Hello... Having an annoying issue with the FNB banking app... I opened an easy account at the Glen branch...! Everything was sorted... Then when I got home and tried to access the app... I couldn't get the OTP number send to my phone! I went to the nearest FNB ATM which is at steeldale pick n pay but no options to change my cellphone number as I noticed on the app the international dialling code is in from of my number... I am in a wheelchair so it's not as easy for me to just go where I want when I want! I have phoned FNB but I'm just told to go to an ATM... Can I please get some assistance?!?!