Losing an old client for good

I'm working abroad and took out a contract with mtn for my mother in order to stay in contact with her. Now I've been with mtn since I could remember. So time has come for us to upgrade and I asked my mom to go into mtn to find out what the upgrade options are for us as I wrote a letter of attorney over my business with mtn and so on. So she went in and was told that we were in behind with our payment of over R6000. So my mom started paying money into to cover up the so called money that was behind, as she was refused to have a statement because she was not allowed to have any say over my contract. She went to another mtn shop who actually helped her and did a recon for her. They found that she was actually not in dept but mtn owe us a couple of thousand. They've send the notice to head office and then her service was terminated over the weekend. She went in to the shop where they sold her prepay sim card with another number until this issue is resolved. Still not a word from their side and the person who actually do help people is on leave, so back to square one again.