After hours my iPhone 4 finally activated but I can't get data to work. I've tried all the network settings, resetting the phone, resetting the network settings, switching 3G on and off etc. And no data without wifi. Anyone else having or had this issue?

After hours my iPhone 4 finally activated but I can't get data to work. I've tried all the network settings, resetting the phone, resetting the network settings, switching 3G on and off etc. And no data without wifi. Anyone else having or had this issue?

I had the same problem, my voice plan was working but my data didnt want to work without wifi. I went into "Settings->General->Network" and kept flipping the "Enable 3G" and "Cellular Data" switches a couple times. I tried couple different combinations of "On" and "Of" and than put them both back "On" and tried again and it started working. Try something like that and hopefully it will work for u too! (I'm on fido). Good luck!

I found out the source of my problem. Last month I jailbroke my 3g and it messed up a file relating to carrier data, even when I restored to a non-jailbroken 4.0 I had lost mms.
I guess this corrupted file stayed in my backup file so restoring my iphone 4 from my 3g backup caused it to copy over the corrupt file. Along with losing mms it made the iphone 4 cellular data not work. There's a lengthy solution to fix it while keeping all your data posted on the macrumors forums involving restoring from backup a couple times & modding/deleting files etc. but I went the easy route and just restored and started fresh not from a backup. Problem solved.