How do I record payment when a customer has already given me a deposit?

I am charging a customer $120/month for exterior rodent control and they paid me in full for the year. I applied that payment to the account but when I try to record each months service off of the credit, I can't seem to be able to. Jobber is telling me that the invoice must exceed $0.50. The balance is showing on the account but I can't figure out how to make the monthly charge come off of the balance. HELP!