7 day exchange period is only actually 6 days

I bought a phone from pep last week Sunday just before 13h00. I then realised when she switch the bluetooth off the phone automatically restarts. So I took the phone back yesterday as according to me it is still within its 7 day period. When I got there they told me that the 7th day was on Saturday and they can send it away to be repaired and can take up to 6 weeks. Which means my daughter will be without a phone for that period. I have spoken to so many people at pep but they just say sorry but that is the way it is. Why is there 7 day return policy only 6 days?