MetroPCS has a 30 day return policy for defective phones, which it sounds like you have. As
@biledigger said you shouldn't have a problem.
"The first option is a free in-store exchange within 30 days of purchase. If the cell phone doesn't work properly when you receive it or stops functioning for any reason covered by the warranty, you may return it for a free warranty exchange within 30 days of purchase. Just bring your cell phone to a MetroPCS store or authorized dealer and if the problem is deemed to be in warranty, an exchange will be made. If the store doesn't have the same phone in stock, a replacement phone will be mailed by the manufacturer to the store for pick up, which can take up to three days."
https://www.metropcs.com/support/shopping-online/shopping-online.html