How to create a subscription that locks someone in for a set period of time?

[RustyCurls]

I'm trying to create a subscription that will lock customers in for a set period of time.

Due to the nature of my work clients agree to a 4 month commitment before it moves into a non-commitment monthly charge.

Right now it looks like subscriptions can be cancelled by the customer at any time.

Does anyone know how to do this?

Thank you