Bad treatment

I have a Vodacom Customer for a long time and I am truly saddened at the recent turn of events. I moved to South Korea on 28 August 2015. I have been trying to change my debit order date since then as my salary date changed. I still have record of all my attempts, and my attempts to sort out this account and exchanged correspondence with Vodacom. Its too expensive for me to phone and be kept on hold. I made large payments in an attempt to bring my account up to date, to no avail. I constantly receive payment letters. FINALLY, 5 months after I moved here, a customer service rep assisted me in changing the date and assured that everything was sorted out and my payments will go off without any trouble, i was relieved when my payment went off as arranged. To my dismay, I received a letter stating that my service was cancelled due to NON-payment and legal action will be instituted against me. They demand full contract payment. I am so dismayed that after all my efforts and payments I am still treated as a deliberate defaulter. I tried sorting it out by e-mail, AGAIN, but received extremely rude feedback and no assistance with my problem. I feel so helpless!