Incorrect billing and call center systems nightmare

IVE BEEN TRYING TO CALL THE MTN CONTRACT LINEL TO SORT OUT MY BILLING QUERIES BUT EVERYTIME THEIR CALL CENTER AGENTS KEEPS TELLING ME THAT THEIR SYSTEM IS OFFLINE AND I MUST CUT THE LINE AND PHONE AGAIN. WHEN I PHONE AFTER HOLDING FOR 30 MINUTES I STILL GET THE SAME RESPONSE. THIS IS COMPLETE BULL**** AND I DESERVE A BETTER SERVICE TO THIS MICKY MOUSE OPERATION THAT IS HAPPENING IN THEIR DEPARTMENT. I WANT THIS ISSUE TO BE RESOLVED BEFORE MY NEXT DEBIT OR THEY CAN TAKE BACK THEIR PHONE AND CANCEL THE CONTRACT