Terrible Customer "Care" service - they just collect pay cheque each month - don't give a damn

I was sold a data contract but they did not stipulate that only 3 routers at the time would work for the contract and each router cost a fortune. I then tried to cancel the contract - after MANY MANY emails - I paid a cancellation fee - this is after eventually taking out another contract with a router - so they combined the two accounts. I paid the lumpsum to cancel but they did not apply it and cancel first contract, now they suspend my services because they keep invoicing on old account - I've emailed SO many times and they do nothing. Absolutely useless.