Some home warranty plans will have something called a service request fee as part of the basic plan or platinum and gold plans as well. The service fee is the price you pay for a repair technician to come to your home and take a look at the issue.
This is standard across most plans, although some will call it a deductible instead of a service request fee. When looking at your coverage options, you need to make sure that you consider these costs.
Most plans like First American Home Warranty and AHS won't charge you if the service technician needs to come back out to the home to repair an issue again.