Faulty Galaxy s5

I took out a contract phone on 1 March 2015 for a Samsung Galaxy s5 on a smart plan 100.<br> I was happy until yesterday 15 March 2015 when the phone just died.<br> I took it back and was told it had to be taken in for repairs for about 21 days.<br> Why should I be inconvenienced.<br> I have 24 months still to go, which makes me very worried that I will be paying for a phone that would give me problems.<br> I asked for the phone to be replaced and I was told that they couldn't.When I asked for the contract to be terminated I was told that the 7 days cancellation period had passed.<br> <br> Im feeling very frustrated as I don't understand why as a paying customer I should be treated in this manner.<br> <br>