Giving paid plan costumers discount on services.

I have hard time figuring out how to implement a simple function in WIX.
Im building a website that provide online tech support services charging per hour (1-to-1 appointment).

I want to create a paid plan or paid subscription (for one year) were the costumers get 25% discount for that service if they have an active plan.

Is this even possible in Wix?