Cancellation of contract

Please assist my dad on this matter. he took a contract and it has now expired which he also sent a letter to cancell the contract. But now he has been told that the letter has been received but the contract cannot be cabcelled in writing. You guys are threatening him about the outstanding amount. That amount will not be paid as he did send you a letter and you confirmed that you have received him. Kindly contact him back on *** and apologise for those harassment calls