IPhone 5 broken lock button?

I few weeks ago I realized that my iphone 5 lock button isn't working. At first the right side completely wouldn't work and I had to click the left side. But now it doesn't work at all. I was wondering if I could get a new phone for free under the warranty? Is this a common problem? Please let me know! Xx

I don't know about the warranty thing, but I do know that this is a common problem… What most people I know do is go into settings>general>accessibility>assistive touch>on