Altech Netstar didnt cancel my contract after 36 months of agreement and want me to pay

Altech Netstar didnt cancel my contract after 36 months of agreement and want me to pay. are you not suppose to notify me or terminate the contract once the agreement is done? why do you keep on sucking up more money even after the contract term has elapsed. i am not going to pay for something that is out of our 36 months contract. the information i got from oarkhurst was that the contract will expire after 36 months.