Unlocking a T-mobile LG optimus L9?

[DerekEe]

I am in urgent need of a new cell phone (preferably an android smartphone) and i have AT&T. Unfortunately, all the phones available are either out of my price range or not what i'm looking for. Finally, I found the LG optimus L9 (a T-mobile phone). But, as i said i am currently with AT&T. So i plan to purchase it, unlock the phone and solve my problem. My question is, will unlocking the phone cause any trouble with it? (Usage of mobile data, voice calls, text messages, signal strength, etc.)

[JARED]

There's a slim chance, a ton on unlocked phones (i.e. LG Nexus 4) have the same effect