Carrier draining battery?

Hi,

I have a 3 weeks old iphone 5s and a friend who has 1 year old iphone 5. Today we used the phone in the same way for the same amout of time. My 5s went from 100% to 16% in 2.53 hours and his 5 went from 100% to 66% in the same time, thats a huge difference. We are using different cariers, in that time i had 1-2 Lines and constantly my phone switched from 3G to 2G and he had 4-5 lines on 3G. Could this eat almost half of my battery ? Or my phone has a problem?

Thanks