Updating of contact details

I recently changed my contact number and I have trying for almost 2 months to change it. My old number now belongs to someone else and all my personal banking notifications is still being sent to that number. I have tried updating the number online but am unable to do so. I cannot even get my account verified online on the app. I tried calling but no one answers the phones. I cannot even do immediate payments as this requires an OTP which gets sent to the old number. I am seriously not able to go into a branch to have this done. What is the purpose of having the app or an online profile if you cannot really do anything? I am really frustrated and annoyed at the lack of service that Standard Bank is providing.