Please change my number

I opened a bank account and obviously used my current details. I received an email with my account number but when I tried to sign in on the app I noticed the otp is going to my cell number that I had 20 years ago!!!! I opened the account with my current details!!!!

I called the call Centre and R50 later I still did not speak to human, I even tried the call me back option but still nothing.

All I want is for Standard Bank to change my number to the number I used to open the account, I don't want to hear about an account I had 20 years ago or I have to go into a branch be that would be very inconvenient. Please change my number so I can sign into the app