No service and charging a higher rate!!!

We cancelled 3 contracts in late November and beginning December. I received and invoice and after speaking to a Consultant I was informed that none of the contracts were cancelled and that he is cancelling them now and I must use the date before the end of the month. I have destroyed the sim cards!! I am not going to pay for something because your staff did not do their jobs and cancel my contracts!!!! Then you are also all of a sudden charging me a higher rate. Seems like you are trying to make extra money!!!