Mistaken Pass Order

Hi!

I took your advice to buy the JR Sanyo-San'in Pass for 7 days to cover our Fukuoka, Nagasaki, Saga, Hiroshima and back itinerary. I found out in my research however that I should get the JR Sanyo-San'in Northern Kyushu Pass to be able to use this for Nagasaki. In my haste and distraction- I clicked on the Sanyo-San'in only and paid for it. When I checked my payment - it was in utter horror that I realized I made a mistake. I contacted the company immediately(within an hour) but they do not want to honor an amendment as I was not canceling but amending. The amount was for 3 Passes. The question, can I get a refund with a penalty if I exchanged the unclaimed Pass when in Japan? Or exchange it for what I need and add the difference? I read a lot of sites, including yours, honoring refunds when not exchanged into the Pass yet, with certain penalties. I'd still like to buy the Sanyo-San'in Northern Kyushu for 7 days- for the freedom to roam around with just one Pass. Thank you very much for your insights!