keep on suspending accout

Mtn keeps on suspending my account after I have paid them via internet transfer every month. Already gave them my bank acc nr twice for debit order and still nothing happens. I have to email them the proof of payment every month before my line gets activated then collections tells me I have to wait for 5 working days for them to allocate the payment and then my line still stays off. I have already threatened them with lawyers and still nothing happens. The latest lady I spoke is known as linda makholwa at customer care. I also sent her the proof of payments and she said she will sort it out, this was more then a week ago. I keep on sending her emails then she opens and reads them but never replies. this problem has been going on for - 5 to 6 months now. I am totally fed up now and I don't know who to talk to anymore.