MTN The Glen poor customer service and ********* business practices

I renewed my cellphone contract at MTN The Glen. I was advised that I can return the device within 7 days if it not working and then they will immediately replace it with a new device. A day or so after I received the Iphone 8 I struggled to hear when I received incoming calls, My son returned the the phone to MTN on my behalf within the 7 day period and they refused to replace the phone making statements that the phone fell. The phone was taken back after the 7 days and once again they refused to replace it because I did not return it within the 7 days period. They give you faulty devices and are not meeting their end of the contract by replacing the phone as promise. When you speak to them on the phone they have an attitude and are not willing to help you