PEP STORE NOT FOLLOWING CONSUMER ACT

I purchased a simple Nokia phone on 6 January at PEP Cell Phone at Hillcrest corner for my 88 year old mother. I was advised that I had 7 days in which to return the phone if anything was wrong to swop for another phone (not the money back as per the consumer guidelines). As we were home on holidays my mother didn't try to use the phone until the evening of the 7th day when we discovered the phone just switched off when she tried to answer a call. We took it back to PEP thinking that we would be able to swop for another phone since it was still brand new. Unfortunately when they saw that it was day 8 they said they would have to send it for repairs. I argued that that's not what the consumer act says but was unable to to sway them that what they were doing was wrong. Eventually I had to leave the phone to be sent for repairs. They called me 2 weeks later to say the phone was back - I went that week-end to collect and said before I leave the store I wanted to check that it was in fact repaired. I called the phone and no surprise here - the phone was NOT repaired. It switched off as the assistant answered which is what the phone was brought in for. They then said I should leave the phone again and they would send it back for repairs.... well today is the 11th February, more than a month after I took it back as it was broken and I still do not have her phone. She is alone at home now with no means of communication. I need PEP to advise how they can make their own rules with regard to how they will deal with faulty goods. I need a new phone for my mother or my money back.