You must locate the supply valve to shut the water off your shower. Regarding showers and bathtubs, you should search the area around the shower or bathtub for an access panel. It may be on the opposite side of the wall from the bathtub or shower.
If you can’t find this valve behind the access panel, you have to look for it either in a ceiling access panel on the floor below or in the basement.
Shower bodies normally have built-in valves to cut off the water supply. Once the escutcheon plate has been removed, you will have access to them.
It depends on whether the contractor bought and fitted a valve with stops. This is a requirement in any building that is over three stories tall.