OTP number update

I lost my phone and could not do a sim swap as I could not recall the 5 numbers I last dialled. This happened at the beginning of Feb this year, I went to the branch to update my contact number and to change my OTP number which I was assured it was done. I have been to over 5 different branches just to do this and it still has not been done, every time they tell me it is done and should take about 1-2 hours before the OTP is changed. To this day I cannot do anything on their app, it still sends the OTP to my old number, I cannot do anything, I cannot see my finds, cannot transfer funds between my accounts or to anyone. THE WORST BANK EVER, OLD DOES NOT MEAN EXPERIENCED!!! Their systems if they have any do not work at all.