Unhappy customer with Ackermans services

I have been a loyal customer of Ackermans clothing for so many years and am very very disappointed. I bought a cell phone and was told if you unhappy or its faulty you may return it within 7 days. So it was faulty and took it back as I bought it on the Saturday the 30 July 2022 and returned it on the following Saturday 6 August 2022 and they refuse to exchange it because according to them the 7 days are passed, can they not count. How is that possible and is so not fair as it is within 7 days. I am currently sitting with no phone as it was booked in for the fault and not exchanged because as per Ackermans it is not returned within 7 days. If you count the days it doesn't make sense as 24hours is 1 day. I am very unhappy, disappointed and furious that I could not exchange because I followed the rules and now sitting with no phone. Ackermans has now truly lost a good customer.