non cancellation of contract after 3 phone calls

My contract was due for an upgrade in November 2014, when i called head office for the contract to be cancelled. I was told that the cancellation is successful and hung up. December and January however i was still billed for the mobile and upon a call each month they now exactly what i am calling for and say they just cancelled it. I was promised refunds but as always they do nothing and there customer care is absurd. I would not recommend them to anyone they just don't care about there customers.