Disputes on finance charges

 Hi,
We have an invoice with open balance only pertaining to finance charges. We would like to dispute the finance charges only. But in Dispute Section, the dispute can only be entered on Lines Subtotals, Specific Invoice Lines, Tax, Freight, and Total. Finance charges are not there. If we use Total amount to process credit on late charges, the system prorates the disputed amount between Line and Tax. We do not have overapllication for lines, the credit memo creation fails. How to deal with the situation?

Thanks