Is the Data plan working on iPhone when i use straight talk service

Dunno... is it?

They are not a supported carrier. If it doesn't work, you'll have to take it up with them.

Yes, it works. Right now I'm using my unlocked iPhone 4 with straight talk. If you decide to get straight talk, you should also get a simple mobile microsim ($0.90 on amazon) to change your APN and mms settings (if you use the simple mobile sim do not use unlockit) just follow the swap sim method (google it).

If u go to http://smartphonematters.com/guides/how-to-setup-straighttalk-wireless-data-and- mms-for-ios-6/3/ it will and download from the site it show it allows you to use 3G on a CDMA straight talk phone