Over Debiting

My name is Joseph Mashaba , I owned a contract cellphone from the above mentioned supplier from 2010 to 2012 , I lost my job back in 2012 and sent a retrenchment letter to the supplier for my contract to be cancelled , although the money I owed kept increasing I got a job in 2014 and arranged for them to debit my account and indeed they started the debits on a monthly basis from may 2014 up until this year in may , I called them and spoke to Nthabiseng Pasha and she told me that my account was paid up and that they now owed me R1300 , after 2 weeks I got a call and the person offered me another cellphone , So I asked him about the money that was due to me , they person said it would be credited to the new mobile device , I refused and asked for my money back he said they will refund it and that was in June 2015 , I've been phoning every week trying to get feed back but no one seems to know , the funny thing is that they were willing to credit the money if I had agreed to take a new contract but now that I didn't agree , they dont want to pay me back my money . Please assist with this issue because it has been going on for long now , case num ***6.