If you move your EA First to another VPS you should first do this: make sure you keep the same magic numbers though. Otherwise, when you move it delete the pending orders. This is from preventing you to make any trades unmanaged by the EA.
Afterwards, go to your AWS console and Stop, then Terminate the instance (right click and see the state options). Once it's terminated you won't get charged from that moment on. If you want you can close your account as well from settings.