They dont call back as promised

MTN told me that the Retention Centre will call me back within 3 - 5 working days. They have not called me back yet and its way passed the 5 working days. I would like to cancel mt contract and move to a new service provider as MTN is not working for me. I wont go into detail. all i want is for them to call me so that i can cancel my contract. <br> <br> If you have an SLA or you promise a customer a certain time then do it. thats good business ethics!!!