Most Horrible Service Provider

MTN the most horrible network service provider. I cancelled my month to month router contract on the 11/02/2025, the store failed to follow the correct process of cancellation. The Contract was only cancelled on 18/03/2025 after more than 50 calls that I made to customer care. Now they say I am owing them R2500 for keeping the device with me, of which I sent it back on time, now the device is nowhere to be found.