Refund on both my Samsungs Please!

I upgraded my contract with Nashua to the S4 galaxy. The S4 started to freeze, overheat, have voice distortions and reboot itself. I took it back to Nashua for repairs in September 2014. As there were no spare phones and I am in National Sales and rely heavily on my phone for business, I was forced to buy a new phone. I bought the Samsung S5 cash. Within 2 months of using the S5 the same problems occurred. I took the unit back to Nashua and was told by the gentleman that the phone was faulty but as Nashua was closing he could not assist me. I have since taken the phone in to a Samsung Repair Centre only to be told instructed that I must take a photo of the unit when it freezes to prove that the phone is faulty. I was also told to not do any of the upgrades on the software. Someone called me to evaluate the service I had received and I explained the whole scenario. I was asked to take the phone to Edenvale for an assessment. There I was very rudely redirected to the repair centre in Boksburg. I have been shunted around from place to place, wasted my time, my petrol and I am still sitting with 2 x faulty Samsung units and have lost complete faith in Samsung products!!