Set off Unearned Revenue

Set off Unearned Revenue

Hi,
I would like to get a clarification on the below.

I have an opening balance of BD.725/- in my Unearned Revenue A/c which includes the overpayments of 6 clients. No One of my clients settled his invoices by paying the value of the invoice less the overpayment amount of BD.50/-.
Now I need to reduce BD.50/- from the unearned revenue and deduct the same from my accounts receivables. I am not able to pass a manual journal as it prevents me from passing JV for accounts receivables. 
Please support me with the solution for this. 

Regards
Sijo