How to unlock my tmobile iPhone 5?

I have a iPhone 5 from tmobile that a family member gave me. They purchased it from tmobile but didn't pay full up front. Tmobile has locked me out of their service because the phone isn't paid in full and won't provide me with the amount I need to pay because I do not have this family members account information. Do I need to factory unlock my iphone 5?

Don't they have prepaid

You slide your finger across the bottem of the screen to the right…

Technically Puffs is right, that is how you unlock an iphone, Now if you meant how do you Jailbreak your iphone, thats a whole different question and meaning behind it.

What you have in your hand is stolen property, if the phone has not been paid for and tmobile has locked it so you can't use it until the family member who got it does so, the phone still belongs to tmobile since it is not paid for, and does not belong to your family member who has NO right to give you that phone because neither of you own it. However, if that family member does pay off the phone, it now belongs to the family member and he/she can do what ever they want with it, now if you end up unlocking it, tmboile will know you did and will also know their phone is being used, and you, or even the family member might find a letter in the mail one day from tmobile sueing you for the price of the phone.