Incorrect Cell Number

I have never experienced more *********** service as i have received from Discovery Bank. Prior to them taking over my account, when it was with FNB, I never had a problem with my cell number being incorrect. Now that they have moved over from FNB to Discovery Bank, suddenly I am no longer receiving sms's to confirm transactions on my card. When i initially called to query why I'm not receiveing sms's, they quoted a cell number linked to my account that DOESN'T EVEN BELONG to me! I have been calling the call centre since June 2020, each time speaking to a different consultants, all promising to call me back and escalating the matter, and to date, 11 phone calls later NO CHANGE to the incorrect cell number loaded on my account. All I hear is generic answers from staff who don't actually know what they are doing. I would LOVE feedback from Discovery Bank, who or how I can resolve this matter.