Recording Payment with service charge (not bank charge)

Recording Payment with service charge (not bank charge)

I have frustration on recording payment for invoice. 

So the process flow is I issue invoices, then customer pay to a payment platform called ExpressPay (Wechat Pay), then I have to manually record the payment. Meanwhile each payment cost 1.2% of the payment amount as service charge.

Methods and Issues:
1. Record Payment on invoice
I can go into each invoices and record payment. However, the service charge could only be "Bank charge". There is no option to assign service charge to specific account, but only go into the default "Bank Fees and Charges".

2. Import as bank statment.
Alternatively, I import the payment record like a bank statment. It is quite handy for me to match  the invoice in just a click. However,  it could not record service charge when matching. Also the payment method could only be Cash. Lastly, there are not option to send payment received (thank you note) email with in the matching page.
In order to record service charge, I add rows in the statment cvs and setup transactions rules, so this part works fine.

Best practice? 
Is there any best practice for my situation?