You would news a Straight Talk SIM card. Why get a T-Mobile SIM when you are trying to run on ST?
Plus ...I thought ST was US only?
The data configurations would be the same tho.
Well, it's a UK phone that has been on Orange. The phone will now be in the US. I'm told Orange is T-Mobile in the US. Straight Talk offers either AT&T SIMs or T-Mobile SIMs, so I think I need the T-Mobile SIM since T-Mobile is Orange in the UK, and this UK phone has always been on the Orange network.
Hope that makes sense. I'll probably be jailbreaking it anyway, which I think lets me unlock it? So maybe it doesn't matter anyway. But on the Straight Talk site when you order a SIM, they're very clear about there being AT&T SIMs and T-Mobile SIMs, depending upon which network the phone you're putting the SIM into is from.
I think whatever road you take to get there, it still uses the same towers. I have an iPhone 4S locked to AT&T and will be using the AT&T Straight Talk SIM in it. My fiancee's UK Orange/T-Mobile 3GS, with the T-Mobile Straight Talk SIM, should still be using the same Straight Talk AT&T towers as my phone.
At least, I think this is all correct, so I hope that someone can correct me if I'm wrong and tell me how to do it! For her 3GS to work with the AT&T SIM, I think it would need to be locked AT&T. But, again, maybe it won't matter since I'll probably be jailbreaking it anyway to get her MMS working (and therefore unlocking so it works on any network?)