Refund due

Cancelled my contracts after 24 months, due to bad services. I was advised that they would charge me for a month and work out what they need to credit me. Received my statement on the 02/01/2016 after my contract termed on the 07/12/2015. My statement reflected they owned me a credit. I phoned on the 02/01/2016 and requested my refund of which I was advised it will take 72 working hours, nothing happened, phone after a week, was advised 21 working days. Phoned numerous occasions and was then advised I was refunded on the 15/01/2016 advised the team leader I was not, and was advised they will provide proof but it will take 10 days to reflect in my account. Checked in my account after the 10 days and still no refund. Logged a call on their system advised I must send my bank statement to escalate the matter, I am not willing to do so as clearly they never paid the fund over to me as they can't even provide the proof of payment from their side. When you request them to phone you back they never do. The team leaders advise they will email you and still nothing happens. Even after you log a call to refund they still phone you to sell their products put can't even refund the money.