Payment update not reflecting

I am a loyal customer of Mtn for the last +/-5yrs and I have not experience anything of such a nature. I made a payment on the 3July at the Absa bank where the Mtn account is held in the hoping that all will be fine. To my surprise up till today that payment is non existent even after I took time off earlier from work to go to 2 branches to take my proof of payment get it emailed to there accounts department. I was promised by the consultants of these 2 stores my account will be updated. It was just a here say,im being send an sms from Mtn wit a big outstanding balance for a phone that I didn't use for that period. Why cant Mtn see my payment????? Why are they robbing me??? ive send through my proof of payments from there own stores twice??? What did they do with my money???