Same here. I'm a light user and my phone barely lasts 4-5 hours a day with brief web browsing, texting, music etc.,. My iPhone 5 and 4S could easily get 7-8hrs with my usage. Spoke with tech support and T-Mobile is sending me a replacement next week. Fingers crossed!
Make sure you are getting brand new one. because i originally got the first one this monday, and then i found out it was refurbished one.
i was like, why am i getting used phone when i'm paying full retail price..
i talked with one of rep on the phone yesterday. and she agreed that i deserve the new phone. so i'm receiving my second one today.!