Incorrect device, cancelled contract and still waiting for Telkom to collect

I ordered a cellphone device from their online service its was a contract deal in November 2017, the device was delivered and unfortunately it was the incorrect device. Thereafter i went to a Telkom store in Centurion to return device and cancel the contract i was told they could not help me or they cant take the device and I must call their call center to arrange the device to be collected and cancel the contract. I have been calling the call center since last year and they have been saying they will arrange for the device to be collected and the contract to be canceled, meanwhile they are debiting from my account for a cellphone that I am not using every month and i keep having to reverse their debts and this will affect my credit score in the long run. It is almost the end or March 2018 now and i have been sitting with a device I do not want and am not using for 4 months and I am not getting assistance from Telkom in rectifying this.