Don’t use MTN!!!

I upgraded my data sim in Oct. my payment should be R299 monthly but my bill is over R1000 which was debited on 1 nov and current bill is the same. Have proof that MTN customer care admits I was incorrectly billed. Still struggling to get my refund and account to be corrected. Last I was told the matter would be investigated. After it was resolved. Going around in circles all because MTN is useless