MTN is *******!!!!

My contract has ended. MTN sent a bill of R70 and I paid it. I went in March to cancel my contract. This morning my phone is blocked. I am told I am in R419 areas. Went to MTN store I was told they can not help me because they have changed their systems so there is nothing they can do. Mind you this is a number I use for business I can’t make call, nothing!!! I am ****** upset!