OVERCHARGE / itemized billing / my number on somebody else's account

I changed to unlimited voice package on 30/11/2020. Today I received an invoice charging me for the UNLIMITED package AND phone usage. Previously I received extremely high phone usage bills and requested - and was promised - itemised billing. I also receive sms monthly for somebody else's account on MY phone number. I even emailed the MD of MTN, Calvin Collett re this, but the problems have not been resolved.