There is no method, they're watching usage, and closing your instances for violating rules.
There is no (worthwhile or profitable) method. You could keep creating new accounts with different credit cards until you run out of card numbers every time you get banned, but that probably won't last long unless you have a long list of credit cards (and by then you would already have to be a fraudster).
Just do it the legitimate way like everyone else does and buy some mining hardware while paying for electricity.
