1. Log in to Alipay account, enter the "Bill" page, check the installment record, and confirm the installment amount completed and the remaining installment amount.

2. If you have completed all the installment payment, but still receive the dunning information, you can try to contact the fitness training institution to confirm whether you have received all your money.

3. If you find that there is a problem with Alipay installment payment, you can try to solve it through Alipay customer service channels. The specific method is: open Alipay APP, enter my page, click the customer service and help button in the upper right corner, and choose online customer service or telephone customer service for consultation.

If the above methods can't solve the problem, I suggest you go to the local consumer association or the court to consult the rights protection.