VODACOM NOT PAYING MONEY BACK

Vodacom took R9600 from my account.I contacted vodacom and they told me this was a cancelation fee for a contract that I had taken out 4 years ago and never upgraded.They said that they would pay the money back within 7-14 working days.After the 14 days i phoned them back to ask why the money had not been paid back.after i had been put on hold and cut off 3 times they then told that they had passed a credit on my account.I then asked who they credited as i no longer had an account with them,this they could not answer.they promised me i would receive the money with 7 working days.I still have not recieved the money and the bank account they withdrew the money from has gone into overdraft when they withdrew it so now I have to pay the interest aswell for a mistake on vodacom's side.