Online banking is a total failure

So FNB decides very suddenly to not send me SMS's or OTP's anymore. I go in to the local branch on the 1st of June 2019 where I have to phone online banking and change all sorts of things on my handset. Amongst other things, I reset my cell number on the ATM as they confirm that it is the correct number they have. Then I am asked to delete all my blocked numbers. As it has already been a very lengthy call, I say I will do this at home as that process will be quite long and then try again. It still does not work. Back to a different branch. Another lengthy phone call. I'm told it will be escalated and will take 24 to 48 hours and online banking will be in touch with me. At least this time I get a reference number. Not having received any communication of any sort, I try again this morning still with no success. Back to the branch. After another 40 minutes of phone call to online banking I am told it will be escalated, it will take 24 to 48 hours and they will be in touch. I must believe this? Nothing wroing with my handset. I get SMS's from other instances but the very important thing, which FNB pushes, online banking, I am unable to do.