Not following terms and conditions on phone policy

After just buying a phone at Mr price ,came home checked phone out again ,checked the quality ,charged phone and it heated up extremely fast.Decided to take it back today to refund or change for different phone .As I am not happy with the phone..They refuse to refund or change.On the terms it says you can return phone within 7 days or change for another with same amount .However they refuse to change and it has only been one day !! It is ridiculous ,I want my money back and they just say that it the rules.There was no explaining of not being able to bring it back at all.