Contract paid up, now getting a run around after I was told I have a refund due to me

My experience has been very bad, I paid an amount of R500 as a final payment because my term of 24 months has been reached, after a payment was made, I kept receiving messages threatening me about being black listed because I did not pay, on the 6th Oct i contacted the customer service line where the agent informed me that the payment did reflect and in fact they owed me a refund and that she had logged a query and someone working on the refunds department would contact me to get my banking details within 7 days. So since no one had contacted me till today, I called the customer service department again and spoke to the guy named Calvin who was very rude and kept interrupting me, he told me I had to call again tomorrow, I obviously got irritated because the previous agent had promised me I was supposed to get a call regarding my banking details. During the conversation Calvin decided to pretend as though he could not hear me and decided to cut the call after he had told me that they had decided to transfer my refund money to the contract that I had agreed to, for which I am suppose to pay R29 per month. No one contacted me to ask if that arrangement would suit me, had i known that they would decide to take my money without my consent I would have not agreed to the offer of this new contract. Calvin was very rude and unprofessional