Can I insert my t-mobile sim card into a iphone?

I currently have a blackberry bold 9900 but my mum is due for an upgrade soon so she won't be using her iphone 4 anymore. She said I can take it but i'm not sure if my sim card will work in there. I can't get the iphone through contract atm because my current contract is for the blackberry. I'm assuming that I will have to get the iphone unlocked with my sim in it for it to work but does anyone know for sure?

Can i get iphone 4s from us and unlock it in india to use it?

Okay, i've heard of many folks getting the locked iphones from the us and jailbreaking and using it in india. I was wondering what are the procedures to be followed. What and how should i tell my friend to buy it (heard there's a contract or something there), on what contract and is it possible for me to jailbreak? Coz $99 sounds like a steal to me!

How much data for an iPhone?

I want to buy an iPhone 5 within the next couple months but I have no idea on how much data to get. I'd prefer to get Verizon, however their plans are the most expensive. I'm thinking about the plan that has unlimited call/text and 1gb of data. I've never had an iPhone or smart phone before so I have no idea how much I'd use it. I'd mostly be using the data for twitter, facebook, email, and occasionally checking sports scores/instagram. However that plan is $90 while for that same price I could get 450 messages/unlimited text/3gb of data with AT&T. What's the quality in service difference between AT&T and Verizon? Would it be worth it to get the two extra gb of data from AT&T?

Is it possible to unlock iPhone 4?

My friend gave me her iPhone 4 32GB because she upgraded to an iPhone 5. Her iPhone 4 was recently upgraded to iOS 6.

I know it's possible to unlock the phone on the previous OS, but i was wondering if it's possible to unlock the phone on the new update.

Anyone have any idea? I've never owned an iPhone. I've been stuck with a silly slide-phone for a couple years.

Any help is greatly appreciated!

Why is itunes deleting my music?

When i sync new music to my iphone, it automatically deletes some of the songs that were already on there, and i get frustrated, if i put a new song it means some other amazing song is going to be removed. Why is this happening? I have an iphone 4, and its updated and everything