Faultu Samsung S5 mini

I had an upgrade in Nov 2014, since receiving my new cell phone, it drops calls all the time. Was in for repair in Jan 2015, only got it back mid Feb 2015 and they say that they have repaired it, but it still has the same problem. Spoke to Marais in Pongola, they say I must talk to head office. Called them and they say I must send it back for repairs!!! This is a brand new phone, why must I be happy with a faulty phone, that has to be repaired 3 times before I can get a new one? In the mean time I am without a phone and I still have to pay. This is unacceptable.