Battery issues, 1% a minute

Hello, i have a new iphone 7. Maximum capacity says 100%. Supposedly the phone was new when i bought it even tho certain settings indicate different. Anyway, when I use phone it dies 1% a minute. I turned off background refresh, did every thing possible. My brightness is always low btw. And still whether its browsing via safari or just music, my phone dies 1% a minute. Every iphone I had does this. What can be the problem? Im scared to get another battery because it the sane issue happened id be so mad id probably break my phone.