I have a AT&T Samsung Galaxy s2 i777. But I have it with Walmart Family Mobile service which doesnt offer 3g/4g. Its Gsm unlocked and I don't pay for 4g. So if I want to use internet, either I use my regular network, or I have to use a local unlocked wifi. Is there any way to force unlock, or somehow use my 4g? My phone is rooted if that helps.