Take it to them if you put it at the curb you will have to pay for it, and they will send collection agencies after you. Don't make your life any more difficult than it has to be.
This is the sensible advice here, they have a diligent collections group, get it out of your life without letting them in.
I dont understand why anybody that planned to live in a house more than 5years would rent any appliance, payback on average water heater/ water softner/ furnace is 4-5 years. Sure they offer no charge service, most of this stuff runs over 5 years without needing service. You can be assured the companies selling contracts are in it for profit not for savings for you.