How can we make payment on the dues that are paid in advance by other departments?

Hi all,

I have a question and I will give you a scenario about our project:

I would like to seek for your expertise and advise about my project - Gasoline Station with 3 Stores

(1. Fuel,     2. Services/Repair    3. Mini grocery) 

The customer's due from the 2 stores (Services / Repair and Grocery) were being paid in advance by the 3rd store (Fuel).

Ex. I have a customer who purchased from the Grocery, and availed Fuel and Services / Repair as well, technically there were 3 invoices from my 3 stores. What I’m doing is that I will get a cash from my Fuel store and pay the due of that customer to my Grocery and Services / Repair. So I will close the invoices from the 2 stores by using the Mode of payment - Advances from Fuel. But I will still send Statement of Account to the customer showing his/her due from my 3 stores but the payment should go to Fuel alone since Fuel store already pay the customer balance from 3 stores in advance. This client will pay me in 30 days or so.

Now the problem is, when the customer pays for his/her total due for the 3 stores I wanted to apply the payment once. How can I do that in my Fuel store? I cannot search for the customer anymore since there is No Open Invoices already ‘coz it was paid in advance by my Fuel store. I don’t want also to look one by one to open the invoice where he/she got the cash from to pay for the advance.

Can you help me think of solution or work around here or should I say that this is not possible and should not do advance payment on behalf of the customer?

Thanks in advance for the response/advise.