ignoring the guarantee

My wife bought a phone from pepstores cellular and its been giving problems since day one. She bought the phone on a wensday and returned it the following wensday. The lady behind the counter told her that she had to come back the following day as the staff who is working there was not able to open the safe. She then returnd the following day and they told her that the problem is the battery and change it for her. Today she went back and this time I went with and asked for the manager witch wernt there. I asked for a new fone as this one was faulty from the beginning. she explained that my wife could not get a new phone because she brought it in one day to late because apparently the day you buy it, even if its late in the afternoon counts as the fist day of the guarantee period. I have maild them and try to phone them and it seems I am being ignored. Pepstores feels nothing for the CPA of south Africa nor for customer service