Can't use the app to change my CC

I have an expired credit card on file with MTN. I can't use the MTN app to change it to my new card, so I continuously get charge attempts (monthly) and then reminders of my badness. All the way through covid, MTN's advice is to drive to them to get my card changed. I keep paying manually because your software and systems won't let me just change to the card I keep using to pay you without interrupting my day to drive to and then present myself physically in your store in a pandemic.