Anybody who has premium account, can the user open a free account too. In other word, the same e-mail will be having 2 account one free and one paid (Premium).
no this is not possible. You can open an account under a different name, different mailadres and also you have to use a different ip. pbxes will also not allow you to register from 1 ip to the free and premium account. When the notice this the free account will be shut down. Also take care that when you open an account for a friend don't use your mailadres and ip, but use his.
So It means you can open 2 or 3 Premium account with same E-mail and IP address to be used for you and your friends if required., is it correct?