I am currently using an iPhone 3G with an upgrade to 4 in the VERY near future. Please tell me this works!!!
Do you mean upgrading your iPhone 3G to an iPhone 4? If so, what do you mean by "tell me this works"? Your upgrade eligibility is determined by your carrier - no one here can know without more info.
If you're asking if the iPhone 4 supports 2 lines - NO.
If you mean upgrading the iOS in your iPhone 3G to iOS 4.1, yes, this works, but not all iOS4 functions are available in the 3G. You may see some slowdown of the phone, though 4.1 is much better than 4.0.
http://support.apple.com/kb/HT4204
Message was edited by: modular747