how do i use a t-mobile phone with at&t?

[xXsuicidalcupcakesXx]

so a friend of mine has this phone that i really want she gave it to me but its tmobile
and i have at&t
so when i put in my sim card it asks me for a network key
i dont know what that is
so can anyone give me a hand here?
is there only one or many network keys or does it depend on the phone?
and if it doesnt what is the network key or how do i find it?
please help and thank you

 

[SandieC]

Call t-mobile customer service. They should unlock it. Possible 10 dollar fee.

 

[geeth]

hi codes are the best method to unlock your mobile .to purchase
the codes visit here mobile-unlocker here they ask the imei number of the mobile .finally they will
send you the codes to unlock your mobile along with the instruction about how to use the codes in your mobile.