According to the Disney Annual Pass Terms & Conditions at Walt Disney World Resort, annual passes, once purchased, are nonrefundable. With your annual pass payments, those cannot be canceled and the installment agreement must continue until your pass is paid for.

No, you cannot simply cancel a Walt Disney World Annual Pass mid-year if you are on the monthly payment plan. When you purchase an Annual Pass and opt for the monthly payment program, you are entering into a legally binding 12-month contract. Disney’s official policy states that passes are non-refundable and non-transferable. While you may have the flexibility of paying in installments, you are still obligated to complete all 12 payments until the end of your pass term. If you wish to stop being an Annual Passholder, your only option is to wait until your renewal window and choose not to renew for the following year. In extreme, documented cases of hardship (such as medical issues or permanent relocation), you can attempt to contact the Annual Passholder dedicated line at (407) WDW-PASS to speak with a Cast Member, but exceptions are extremely rare. For most guests, the monthly plan is simply a financing tool, not a "subscription" that can be toggled on and off. If you stop your payments without authorization, Disney may block your ability to purchase tickets or passes in the future and could potentially refer the balance to a collection agency.