Palm to Unlocked 3G: Getting data to work

[bobsetzer]

I'm new to the iPhone but so far, love it.

I bought a jailbroken/unlocked iPhone off Craig's list. It's firmware is 3.1.3 (7E18) and its Baseband/modem firmware is 05.12.01

I put my ATT SIM in the iPhone from my old Palm Centro. Works fine for voice but the data doesn't work. I have an unlimited plan for data on the Centro ($15.00per month) and was wondering if there was any way to get the iPhone to recognize and use that?

I realize I can go with T-Mobile or Simple Mobile (the point of unlocking, I presume) but the service with those providers is not good in my area. Obviously, I can activate with ATT and pay $25.00 per month for 2 gigs but if i can get Unlimited to work for $15.00 a month, I'd prefer that.

Please advise. Thanks.

[fmlouder]

You have a grandfather package so most likely u will keep it but you probably have the apn settings wrong

[bobsetzer]

Thanks, but what's an "APN Setting"

ATT won't grandfather me because my SIM was originally in a RAZR so it's not a "smart phone" package, though it is unlimited data.