Re: I have lost my internet connection and don't know why. I have wi-fi on with no results.
When you go to Settings/Connections/Wifi, do you see any wifi signals? If not, bring the phone back, the wifi radio died an early death. (It's covered under the warranty.)
If you do, press the one that's your router and see if you connect (make sure you enter the password correctly if asked to.) If it still doesn't connect then, post here again, letting us know the make and model of the phone, what version of Android it's running, and the make and model of the router.
I'm assuming that you're aware that you have to provide a wifi signal for the phone to connect to - your carrier only provides cellphone service, not wifi service.