IOS – Switching to Straight Talk From T-Mobile on an iPhone 5

I am at my wit's end trying to get my wife's iPhone 5 switched from T-Mobile to straight talk.

Just about a month ago my wife's old cellphone was reaching a breaking point, so she decided to get an unlocked gsm iphone 5 16GB from the Apple store. We took it to T-Mobile where they popped in a sim and everything worked perfectly. Well, there's no 1900mhz HSPA+ in our area yet, and she had to edit the APN to get MMS messages working, but perfect apart from those things.

Our contract is up now and she wants 3G speeds so we decided to switch her over to Straight Talk. What I've done so far is port her number over, and texts (non-MMS) and calls work perfectly.

But data won't work whatsoever. It gives the message:

"not subscribed to a cellular data service"

I've tried calling Straight Talk tech support but they try to walk me through editing the APN but now the Settings > General > Network entry no longer shows up! I think it depends on what SIM you have inserted, but the T-Mobile sim we had is long trashed at this point.

What I've learned so far is that if the Settings > General > Network entry does not show up that means your phone is locked (?), but she specifically bought an unlocked phone so now I'm just confused.

Some advice I've googled has said to restore the phone in iTunes, but she had never synced it before switching to StraightTalk. Anyway, I backed up and restored it, but I didn't get the:

"Congratulations your phone is unlocked."

message I guess I should be seeing.

I've also read advice telling me to contact AT&T about unlocking the phone, but you have to fax something? And it takes 5-7 days? Ugh.

I guess I'm just asking how do I get the Settings > General > Network entry to show up so I can continue with Straight Talk tech support and try to get the data problem solved?