Send the invitation to your close frens (doesn't matter mero mobile users or ntc users but I've not tested with the CDMA and UTL users)
--> Then, Register the new account for every fren you invited (by username & password of your choice but cell number of your fren). Do remember to invite the fren firstly before registering otherwise the trick will not work. And you ought to remember the username and password u used to register the new account for your fren, as we would be needing those in our following step.
--> Once, you register the new account, the activation code will be sent to your fren's mobile number.
--> Contact him/her for the Activation Code and note it down.
--> Login with the username and password of your fren's account you just created in above step and enter the activation code. When its done you will earn 0.3 $ credit which can be verified with the sms notification you will get from mig.
--> Do this for as many frens as you want & can. But remember the mobile number once registered couldn't be used again for registeration or more specifically increasing credit with this trick.