How to use iMessage over wifi or 3G/2G.here is a simple trick to How to Set Up and Use iMessage on Iphone 5 in IOS 6. iOS 5, allows you to send unlimited texts over wifi for free using iMessage. iMessage is messaging service that is a combination of both MMS messaging and instant messaging, with the added bonus of sending other iOS 5 users messages at absolute no cost.
iMessage is built right in to the messages app so there is nothing you need to do to activate this feature
Step 1. Start off by opening the “Applications” icon.
Step 2. Scroll down to look for “Settings”.
Step 3. Search for the “Messages.” option.
Step 4. Once there, ensure that the iMessage switch is set to ON. You can also turn on Send Read Receipts and Send As SMS. Note that the Send as SMS option will use your cell provider’s network to send the message, which may charge you an SMS fee if you don’t have a unlimited text messaging plan.
Step 5.After configuring those options, tap on the “Receive At” button to see more iMessage settings. On this page, you will be able to set your active Apple ID. Below that is where you can set email address that others can iMessages. By default, anyone can iMessage your Phone number for free. You can also tap Caller ID to set which email address (or phone number) will appear when you iMessage others.
Step 6. Sending an iMessage is the same as sending an MMS or SMS message on your iPhone before iOS 6.it require Wifi/ internet connection (3g ). When sending messages, the Send button will be blue if you are sending an iMessage, or green if you are sending a standard SMS/MMS message. The placeholder text will also dictate “iMessage” or “Text Message”.