Telkom ******* - took more than R4000 for me only refund R2365

Telkom duplicated my order by sending me an extra device. I reported it immediately. Took them 3 months with several calls in between to collect it. Take note the device was still sealed, not used nor opened. They charged me every month for it for 7 months. Then the battle started for them to cancel the device on the system and refund me. Another 2 months later I get a message to say the device has been cancelled and refund has been loaded. After returning the device sealed and not opened, Telkom decides to only pay me back R 2365 of the R 4017.74 that they deducted from me. When I questioned this - I get told they are only going to refund me for the months I didn't use it......WHEN I HAVE NEVER USED IT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!