Mtn Not willing to assist

Upon going overseas, I was unaware of the data charges of MTN, I used WIFI most of the time, however I ended up with a 7k bill. I gladly made a payment arrangement to pay the amounts in April, however MTN has now suspended my line, upon calling to see how they can help a client who has been with MTN over 6 years, the response I have received was NO PAYMENT ARRANGEMENT RECEIVED - line suspended, now I have a LUMP SUM to pay. All I ask is that you consider the duration of my time with you, and I haven't had this problem before, I have paid so much money to MTN over the years and now they refuse to activate my line and make a reasonable payment arrangement to settle the arrears amount, I was so tempted to go to take the offer from CELL C to buy my contract out and take one with them, but MTN has never given me problems until now, I don't have a problem paying the money off with a reasonable arrangement, but please can you at least activate my line so I have a phone to use. CAN SOMEONE PLEASE HELP ME as this is going in circles, the call center says call Credit department , but you end up in a constant cycle of being cut off and having to retry. Please MTN , help a long serving client!