Shocking Customer Service

On the 17th December my 24 month contract expired. On the 6th December I phoned to convert my contract to prepaid I spoke to Nqobile. I paid R199 at the end of December even though I received no data etc. I purchased data and on the 17th January it disappeared as my contract switched to prepaid. On 1st February MTN processed another debit order for R199 so I reversed it. 1st March another R199 debit order so I reversed that one also. I have written no less than 6 emails to customer service explaining all of this. They have not had the courtesy to reply to one of them . I keep getting sms's threatening my credit rating, for R199 SERIOUSLY!!!! I have had contracts for more than 20 years with MTN and this is how they treat good, loyal customers.