PLEASE HELP!!!

Ive been selling on here for a bit now and have always taken pride in offering true combined postage.

BUT now that ebay charges fees on the postage I have lost so many sales as my customers can not request a combined postage invoice. I have told them to add to the cart (as ebay have told me) but they still don't have the option to request a invoice.
I have double checked my listings and made sure they are not asking for instant payment. 

Its really hard to ask a customer to believe I will refund the difference in postage for them.

I really hope I'm just missing something and I can offer true combined postage to my customers again.

I have spent A LOT of time on line with ebays live chat and everything they say is untrue and whatever they recommend doesn't work.