Do phones in the T-Mobile service use sim cards?

I don't know if all cell phones use sim card, but do phones in the T-Mobile service use sim cards? I have a phone thats unlocked (Motorola E398) and can use T-Mobile, and my friend has T-Mobile.

 

no, just stick a banana up the sim card slot.

lol, i couldn't resist sayin that

 

If a phone can be un locked, means it has a Sims card. Carriers like T-mobile, cingular, etc. operate under a GSM network that requires Sims cards, unlike others like Verizon, Sprint / Nextel who orerate under CDMA networks do not use sims cards.

 

dude how is ur phone i'm planning to get a motorola398 is it good how many song does it hold.