I got a moblie phone for christmas and a got a sony ericsson W910i but when I put in my sim card and batterey I charged it and I left it for 2.5 hours when I turned it on a few minutes later it switched off I tried it several times and it would not work I need a answer o and its with o2 and the sim card is from my old phone bye

Take out the sim card, and then put in the battery by itself, and see if it turns on and stays on.

It doe not work it just says put in sim card

But it's staying on? If the phone is resetting itself when you put in the sim card, and the phone is staying on when you take the sim card out, then there's a chance it may be the sim card. Is the new phone unlocked to handle o2?

My best guess. DOA (Dead on Arrival) battery or weak battery. Charge phone while off overnight.

Yea when I took the sim card out and when it said that a few minutes later it went off I then put my old sim card bac in my old phone and it said insert sim card so I'm going to bring it in2 o2 tomorrow but I do think it is the sim card thanks any way

Try charging it for the whole night switched off, if same problem next morning then visit the store it was brought from as there is an issue with the phone.

Never seen a 2.5 hour recommended charge time. Like above, Charge overnight.