There is no option to disable charging currently. To should be within the limits of free tier to not get charged. And stopping your instance is more than enough to not get charged. In GCP, if you have zero HTTP requests it will automatically stop your application.
Even if you delete your credit card information, you will be receiving bills if there is an unpaid balance.
Amazon will only remind if there is an unpaid balance. When you are using its services it will not remind you when it goes over free tier. You can put a reminder by yourself or you can set up alarms.