The phone is locked to the t-mobile carrier.
To unlock the phone for use with your carrier, you need an unlock code.
If your uncle is still a t-mobile customer, they may provide the unlock code to him for the blackberry.
Otherwise you will need to buy an unlock code from a unlock provider.
"That's it then. Cancel the kitchen scraps for lepers and orphans, no more merciful beheadings... and call off Christmas."