Treating the customer unfairly

Signed up for a 24 month contract at the end of April and not since recently (2nd week July) after countless calls with technical support, an unfruitful visit to cell c on the advise of mweb, a few visits to an mweb branch for assistance, testing at various locations, a swopped out unit, heartache and a few tears - Mweb wants their full 3 months subscription paid out in full. It doesn't seem to matter that the product did not deliver what was promised. On the basis that all the time trying to make use of the service and experiencing incredibly frustrating connection, hours on the phone with technical support, testing, etc. there is usage on the device and according to them, it was by my own preference that I did not make further use of the device. What has happened to treating the customer fairly? Why am I expected to pay for service that failed to deliver what was promised?