@Kushagra Sharma While the rate at which you are charged is by the hour, there is no way to stop the service when you are not using it.
You do however have control over how many instances (SU) are running at a time and these extra instances are charged only when they are running.
So, depending on your scenario, the minimum number of instances that you have running always will be charged for whether they are being used or not.
You can read more about how to manage costs in the official docs.