Will my T-mobile sim card work on an iPhone 4/4S for AT&T or Verizon?

So when I bought an iPhone 4 or 4s unlock. Then I take my T-mobile sim card out from my old phone then put it in the iPhone, will I it work instantly including making calls!

AT&T = Yes
Verizon = No
Sprint = No

T-Mobile and At&t are both GSM Networks. Verizon and Sprint are both CDMA, a completely different type of broad casting signal. You will find that most Sprint / Verizon phones don't come with a sim card.
The only thing is that it's not that simple. You basically have two choices, 1) Buy an unlocked iPhone, or, 2) Buy an At&t iPhone and have it unlocked.
What I did, was buy an AT&T iphone and have it unlocked for T-Mobile

GSM = Global System for Mobile
CDMA = Code Division Multiple Access
CDMA Networks normally don't tend to use SIM cards, which tend to make each phone set up harder, and making transferring contacts much more difficult.

Once you buy an AT&T iPhone, you have to be VERY careful that you have two receipts. One with proof of purchase from apple / att, and one with proof of ownership (if you buy off ebay). Once you have these receipts, you will have to fax them to AT&T and wait 3 days for them to unlock the iphone. You will then have to plug it into a PC or MAC, and it will unlock the phone. Then you will be able to put your tmobile sim card in and it will unlock. Once unlocked, you will have to plug it into your computer and update or else you won't be able to send MMS/Picture Messages.

In rare cases, you can take it into T-Mobile, and they will unlock it for you.

Other than that your iphone will be working fine, and you will be able to make calls just like your old phone.

DO NOT do any type of IMEI Unlock that ISN'T by T-Mobile or AT&T, as these are NOT SECURE! Also don't try jailbreaking because A) it voids your warranty B) It's not the best thing for your phone

Thumbs Up?

An AT&T one will, you may have to change the APN settings on the phone. Google IPhone APN settings T-Mobile for the info.