Call barring

My husbands Sim card has been blocked. His sim had call barring from last week, when calling MTN they said they will remove it , and he shoulld give it 24 hrs, for him to receive and make calls. 24 hrs later his sim was still locked. he went to MTN and was told that he needs to do sim swap, swap was done but then his sim is still not working, when he called MTN customer services they said his sim is under investigation and will only be opened after a month, we cant wait a month as this is a number he uses for business and banking. he has been been using the same number for over 10 years now and it is unacceptable for MTN to do this.