Samsung S6 Terrible Phone

I upgraded my cellphone contract yesterday to a Samsung S6, I had the Samsung S4 before. When I got home the phone restarted itself the entire time, it freezes the entire time, when I phone someone they say they cannot hear me it breaks up, the problems get worse once the wifi is activated and it only shows 1 to 2 bars of cellphone reception. Really a disappointment, I had to return it to the store and now have to wait 5 days for a replacement, which I have no guarantee if it will do the same, if the second one does the same then I am going to insist the service provider change my contract to a Apple IPhone, cannot believe Samsung makes such poor phones, I am so put off Samsung now, next time I am getting an iPhone instead.