Contract cancellation

I was offered a mifi device by telkom only to find out after a month of using the device that there is no Telkom coverage in my area. I contacted the call centre and queried, which they then asked me send through cancellation documents for them to process a cancellation. I did so and followed up several times thereafter. I even took out an ADSL home contract with them as I really needed to have access to wifi. The installation was done timeously but still no response was recieved in regards to the mifi device. I followed up again and all the agents will say is forward documents it takes 21days to cancel. I have been patient enough it is now over 4months since iv submitted the documents but still no response. Today i called once again because without fail the debit order will go off, and was told the very same thing. Im tired of going round in circles as this is an additional expense that I have to manage due to poor service. Extremely dissappointed with Telkom and their "21day" cancellation process which is well over 4months