Strange how you don't have the update showing yet.
I have read that sometimes OTA upgrades don't always show up, but yet if you use KIES on the PC, it will always show the upgrade being available?
Try KIES perhaps?
For what it's worth, I've got a Tmob simcard in mine, and it's a UK simfree handset.
I was notified of the software upgrade(via wifi) whilst on holiday in Las Vegas, with my phone switched in airplane mode (ie simcard off)! So I'm not so sure that the simcard/network has any bearing on the software release dates at all....