I had a new iPhone 6s battery fitted a few months ago. When used simply as a phone, the battery lasts quite well. Particularly since IOS update 12.1.2 the battery drains quite quickly when surfing, - I think even quicker when not on WiFi. Maybe it’s just me, but I wonder if others are finding the same?
Apple did something in the new software update because ever since then I was having the same problem and I thought it's happening to everyone too because my friend told me her iPhone drains battery way too much now. But she sold it and bought iPhone 6s from some website named click here for £149.99 and it's working perfectly. Maybe I should do the same.