Missing Payments

I have two cell phone contracts with MTN SP and I make my payments manually at Absa Bank,suddenly my phones were blocked as I got sms's telling me that I'm behind with the payments. This was around mid June and to me it was surprising as I had last made a payment of R700 at an ATM at Chris Hani Mall in Vosloorus on the 27th May 2015. All this was during the strike action. For over 5years I have been a loyal customer and making payments the same manner and never encountered any problems. When I did follow up at Lambton outlet I was told to bring the proof of payment also the first time EVER this was requested from me. I did that and they said they logged a USD. Then after few I went back for feed back and I was told to resubmit the proof which unfortunately I had lost.I was then sent from pillar to post concerning my account til today,eventually I was told they can't trace it, I even went to absa for print out with no luck. Now what puzzles me is all these years mtn managed to trace payments withou any proof but now suddenly they can't. I have been phoning their legal dept for follow up only to be cut off without getting help. I'm deeply disappointed with mtn,done with them!