Unlocking Iphone 4 for T-mobile?

Is there any possible way to unlcock an iphone for tmobile and put a t mobile sim card into it

If it's a Verizon iPhone 4, it won't work on any other network other than Verizon

Yes you unlock your iphone 4 for using with T-mobile. If your iPhone 4 is locked to USA network and you bought before jan 26 2013 you can unlock it. To unlock iPhone 4 from network lock get the remote unlock service. If you want to remote unlock service you can visit this site http://www.superunlockcodes.com/apple-iphone-4/rs12wp9/ to get the remote unlock service and unlock your iPhone4. Here they are providing sprint and AT&T unlocking service for USA iphone 4. If you bought the Iphone4 after jan 26 2013 it is illegal to unlock without network provider permission. If you want to make it legal you can sign a petition in the Link below.
https://petitions.whitehouse.gov/petition/make-unlocking-cell-phones-legal/1g9KhZG7
The signatures should be signed by 23rd of February. To make it legal you need to wait until 1 lakhs petition to be signed in and approved by USA government. After make the unlocking as legal you can unlock your Iphone4.

You would have to contact your carrier to see if it is eligible to be unlocked.