How to unlock Sprint iPhone and put on T-mobile network?

I have the Galaxy S2 for T-mobile, and an iPhone that used to be my dads for Sprint. I know its illegal to swap phones like this unless you get the carriers approval, so how do i that without making this difficult? I know T-mobile is weird about this stuff but if they don't do it I'm leaving their service cause I don't really like it and this would top it all off. Instructions please.

Added (1). I've seen people on youtube do it. I was wondering if the sim card I put into the iPhone can it be my current phones sim card? Is that what I'm supposed to do?

Can only use a Sprint phone on their network. Doubt Sprint will unlock it or T-Mobile will let you use it on their network.

Unless it is an international phone, it will never work on T-mobile's network. Sprint uses CDMA radios and T-mobile uses GSM.

You can unlock your sprint Iphone by going to this website: www.cellsunlock.com
I use it, and it is very safe and guaranteed
choose your manufacturer
choose your carrier
submit an order
receive permenant unlock code in email in 1-7 days
it costs $119.99 but this is about the best price you will ever find