From today, forcing users to Like your page and give them free internet as a reward is no longer possible. The reason is a change in Facebook Policy:
You must not incentivize people to use social plugins or to like a Page. This includes offering rewards, or gating apps or app content based on whether or not a person has liked a Page. It remains acceptable to incentivize people to login to your app, checkin at a place or enter a promotion on your app’s Page. To ensure quality connections and help businesses reach the people who matter to them, we want people to like Pages because they want to connect and hear from the business, not because of artificial incentives. We believe this update will benefit people and advertisers alike.
Basically Facebook wants users to like brand pages because they actually “like” them, not because they were promised some freebie or contest entry for doing it.
The suggested method now is Checkin/Wallpost which will also grow your userbase. More check-ins and engagement with your Page will improve how it ranks in search too.
And you can still put the LIKE button on the page after successful login and ask people to LIKE your page if they want. But they cannot be forced to do so.
If you are a White Label operator and you have your own facebook app, you need to send it for review to Facebook if you wish to use the Checkin feature. The process is described here (you don’t have to create a new app, you need to edit your existing one!)
If you are using custom skins and edited the main_social.inc.html, you need to make some changes in that template:
Search for this code: