My husband's company just upgraded his phone, which leaves us with an extra Samsung Galaxy S3 SCH-I535 (verizon). My daughter is turning 12 this week and it seems like a good time to give her hubby's old phone. However, it would be a lot cheaper for us to add her to my T-Mobile plan rather than hubby's verizon plan. I put my t-mobile SIM card into the phone and it works to make calls and send texts, so I guess it's "unlocked," but the data doesn't work. Is there a simple fix? An app I can download? I keep reading about rooting, but that sounds far too complicated for my little 12-year old. I honestly don't care if she has lightning-speed data, but since I'm paying for it, we might as well try to make it work. Thanks!