Will purchasing and applying Reserved Instances cause downtime in my production environment?

I am considering purchasing a 1- or 3-year Reserved Instance for our production environment to take advantage of Azure's discount. However, I want to confirm if applying the Reserved Instance through the Azure Portal will cause any downtime or interruptions to the services we currently have running (such as Virtual Machines or databases).

From what I understand, the Reserved Instance applies at the billing level and should not impact the running services, but I want to ensure there are no disruptions before proceeding.

Could you confirm whether or not there will be any downtime or service interruptions when we apply the Reserved Instance? Thank you!