if your iphone 4 doesn't have service can you still use it over wi-fi?
As long as there is wi-fi, and it's either wide open or you have a password to access it, you should be able to get to the Net, for Email, Web browsing etc.Do you know you have the authority to use the wi-fi your machine can see?If you know,you can use wifi.TOPONS.
Only the Internet
Yes you can still use it as a computer; e~mail etc. You can't use it for calling or texting.
If you have a skype account, you can make calls on the net without 3G service.
Yes u can but with limitations. You can not place phone calls unless you use a VoIP application. All other applications that require an Internet connection will continue to work with wifi.
If you mean service from AT&T has been turned off, then no. Wifi won't work either.