Excessive UUSD spam

I have been getting excessive spam from their MTN UUSD messages. I have reached out initially to support on Wednesday, I was basically treated like I was lying and that I had to provide screenshot proof, nevertheless, I asked for the matter to be escalated.

Today, their support basically told me nothing has been done, and no ticket has been created. I was also told to download Truecaller to block their excessive USSD spam popups.

I still haven't receive any solution.