Dell Venue phone does not get internet via cell tower

My phone is on the T-mobile network and I rarely get a T-mobile signal and I usually get a signal from Viaero Wireless so I get all calls and make calls just fine. I do get wi-fi internet through my home router but nowhere else. How do I get internet service to work on this phone? I never see a 3G icon on my phone like I have on my other Samsung phone?