BILLING ISSUES AGAIN

I HAVE YET ANOTHER ISSUE WITH MTN IN A 4 MONTH PERIOD.JUST TO REFRESH YOUR MEMORY I WAS BILLED INCORRECTLY IN NOVEMBER 2015 AND HAD A HASSLE RECEIVING MY MONEY BACK UNTIL I PUT MTN ON HELLO PETER THEN ONLY DID I RECEIVE A SPEEDY RESPONSE I RECEIVED AN SMS IN FEBRUARY 2016 SAYING THAT I HAVE USED 50% OF MY USAGE LIMIT HOWEVER MY USAGE LIMIT IS SET AT ZERO SO HOW DID THIS HAPPEN YET AGAIN I HAVE BEEN PHONING MTN FROM THE 10TH FEBRUARY ASKING FOR AN EXPLANATION AND I GET TOLD THAT THE INVOICE WILL ONLY BE FINALISED ON THE 13TH FEB SO I PHONE AGAIN ON THE 13TH OF FEB AND I GET TOLD THAT THE INVOICE WILL BE FINALISED THE 15TH FEB AND I CALL THE 15TH OF FEB AND I GET TOLD THE INVOICE WILL BE FINALISED ON THE 16TH OF FEB AND I CALL AGAIN AND YET AGAIN GET TOLD THE SAME STORY...I AM COMPLETELY FED UP . I SET THE LIMITS TO ZERO SO THAT I AVOID THIS HASSLE YET THIS IS THE SECOND TIME I AM GOING THROUGH THIS. I EVEN SENT AN E MAIL TO CUSTOMER CARE AND HAVENT RECEIVED A RESPONSE YET. THE SERVICE IS PATHETIC AND THE CALL CENTRE STAFF ARE USELESS. I NEED THIS RESOLVE BEFORE THE 20TH OF FEB OR ELSE I WILL REVERSE THE DEBIT ORDER ON MY ACCOUNT. WHAT KIND OF CUSTOMER SERVICE IS THIS???/