Post contractual obligations

Read the fine print ..or maybe I should say listen to the fine print. I agreed to a 2year contract with a major telecommunication company and diligently paid my dues for 2years. After two years they continued deducting for the next 18months. Upon inquiry I was told that I had to write a letter cancelling my contract. I was astounded because two years had passed and I was no longer utilizing their services. I was informed that after the contract ends it now becomes a month to month contract. I did not know that I had agreed to a lifetime contract. BE CAREFUL A FOOL AND HIS MONEY ARE EASILY PARTED.