Contract cancelation

I have been trying numerous times without any success to cancel my contract. Each time the call centre agents comes up with different internal procedures that needs to be completed before my contract will be cancelled and that i should call back to check if its been completed and then it will be cancelled. How difficult can it be to cancel your contract after honouring it for two years! The call centre has now blocked my number for calling too much. The level of service is pathetic and shocking!