Iphone 4 unlocked on t-mobile?

I have an iphone 4 that is unlocked, I currently have straight talk and it is horrible I get dropped calls and there's a 1 gb data cap. After the cap the Internet is really really slow. I know I an put a t-mobile sim and use their service and Internet but for Internet I hear 3G doesn't work? And your on edge speeds and I have heard some people say the Internet is good and they have 3G speeds and I have friends that say their 3G data works? Anyways with the new tmobile plans 50$ for unlimited everything but 500mb are high speed data, after you use the 500 mb how slow with the internet be?

If i buy a atnt iphone 4 from amazon can i still use it for t-mobile?

My plan for t-mobile is only unlimited texts and calls, no internet.
I want to buy an iphone 4 from amazon that is atnt, but my current phone is for t-mobile. Can i still unlock it and only have internet were there's Wi-Fi OR do i have to have internet in the plan.
Also, can you give me information of the whole unlocking process, because I don't know the whole details of unlocking an iphone.

Added (1). How much will it cost to unlock?

How to track my Ipod on find my Iphone?

My Ipod 5 got stolen at school last week. I went on Find my Iphone to track the Ipod and it worked and everything I made sure that when it was put in Wi-Fi it would play a sound, send a message, and lock it.

But I removed it because I didn't want to have the sound played anymore but now I don't now how to add my Ipod because it says I need my Ipod to it and that's pretty hard since I don't have it anymore. So is their away I can add it with out the Ipod?

How much are otter boxes worth?

Its a all black otter box for a iPhone and its in perfect condition, a friend lived with me for a few months and she just moved back to Mississippi AMD she left it AMD when I told her she said I could keep it cause she bought a new one AMD i'm in Virginia but o don't have an iPhone.

Windows was unable to connect to thomson router?

I accidentally turned my router off today for about 10 minutes (Thomson TG585 v7) and now I can't connect with any device at all, ipad, iphone, laptop, ps3 etc. I've gone through all of the settings in the router to try and configure it but nothing I do works. I've had this problem many times in the past but it comes back on and things can connect again… Sometimes, it's just unpredictable.

I need reasons why to have a iPhone with bad grades

So I've been wanting a iPhone like for school and I told my mom it would pick up my grades! Cause at my school it's high tech! And she was just yelling at me cause in language, world history, math, and science which is my worst subject I have F's and I was telling her what if I bring my Math grade, Language grade and world history grade then can I have 1! She just said Bring them all up and ill get you one and I had a good reason and I promised her I would bring up math, Lang, and world history but no he won't so I need any more GOOD REASONS! Please Help PEOPLE AT MY SCHOOL MAKE FUN OF ME BECAUSE I DON't HAVE A IPHONE!