PEP phones not picking up network

I am dissatisfied with your services at PEP. I bought a phone and later on the same day it had a problem picking up the network until the whole week. Upon me returning the phone I was told I have past 7 days for exchange and they will take it out to repairs.It had been 3 months without my phone which is still at repairs. I even checked today but its still not there. The problem with the phone was manufacturers fault but why should I take my phone for repair as its not my fault. I need a new replacement phone please!!!. The store is in Protea Gardens Mall Soweto