Unfortunately, this is an issue many people have faced. While another user here could invite you to an Education plan, your account would be tied to that plan, not to mention they would be able to see and control all of your workspaces. In other words, that probably isn’t a good solution. The best solution for you would probably be to get a prepaid card from a store with a small amount on it and use that, since you can buy those with cash. Cloud9 doesn’t actually charge you for anything (though it may appear that they have charged you $1, but that’s just a card hold).