Do you have an Azure App Service Plan and you pay even though you don’t currently need the app.
The problem: Azure offers no way to change or stop an App Service-Plan to save money.
But in some cases there is a possibility to save money. If you don’t need more then 1 GB storage, then you can migrate the app to a free App Service-Plan and remove your chargeable App Service-Plan.
Microsoft has documented how to create an App Service-Plan and how to move an app between two service plan here: https://docs.microsoft.com/en-us/azure/app-service/app-service-plan-manage