Yes, there are ways of "fixing" it via jail breaking - but it's quite long winded (you have to patch commcenter, then edit the plists, then force load the plist again). Look for info on the CommCentre patch.
Depending on how much data you use, it might be easier to buy an iPhone 4/4S microsim from TMobile for £10, activate it in your iPhone 4 (this is important), and when you get a text saying your "12 months free web is active" swap it to the iPad. It gives you 500mb a month for 12 month, all for the cost of the initial £10 top up.
Is there a similar deal for T-Mo in the US?