FAULTY PHONE

I upgraded my phone. Took a package deal with a phone and a tablet. When i started using the phone it was faulty. I complained and asked if i can rather have the Samsung phone, the Vodaphone 6 gives problems. So they said i cant cause its a package deal. They will replace the phone which they did. Ever since we started using the phone it freezes up. I mean its a brand new phone and its not working. Im prepaired to pay more on my contract to get a Samsung phone. How can i psy for something that dont work. Please can you help.