Customer Advance

Hi everyone. Just wanna ask I have a negative balance on Customer Advance. I have made an error on my entry. I journalize an entry as Dr Customer Advance, CR Bank Account. And I made a Receive Payment of the pre-payment amount of customer an apply it as DR Bank Account CR Accounts Receivable. After 3 months the invoice is paid and the negative balance of Accounts Receivable is also applied. How will I solve the negative balance of Customer Advance?