I'm with t mobile and I was getting the same speeds as you
Then I found out that t mobile restrict the data speeds on a 1gb bundle .
So I upgraded to the 3gb bundle and now average between 3 to 5 mg . This is
Deffinatley area specific and won't always get such good speeds . this said I'm on a
contract not pay as you go and not on virgin . but it might be worth looking into virgins
data policies cos they could be holding out on you with your 1 gb bundle . hope
this helps