James Allen Claims a wedding band they send us is size 11 when 3 independent jewellers say it is not New York Internet

 So my fiance and I live in Australia but couldn't find the design we liked so started looking online.
We read reviews & went ahead & ordered a James Allen Platinum men's wedding band size 11.
To determine the size we visited Tiffany's in Australia as they have US sizing & were fitted as a size 11. We also went to an Australian jewellers & determined his size & translated the size using the James Allen conversion scale. We then finally used their online sizing guide (using a credit card to determine the size of the screen).
All of these told us size 11.
So we ordered a size 11.
The ring arrived & was lovely. My fiance put it on & it was huge. We were shocked we had ordered it so wrong. We went that night to visit some jewellers who told us the ring was a size 12 & we visited Tiffany's again & confirmed he was a size 11. We visited a third jewellers who recommended we go to the sixe of 10 3/4 as due to it being summer his fingers might go smaller in winter. They said size 11 was the right size for him though. The ring which James Allen claimed was size 11 clearly wasn't.
We dealt with Greg & Melissa & they advised us to send the ring back & they would pay for the $65 FED EX Postage (which they would refund to my credit card)if the sizing was indeed of.
We sent it of & they emailed saying it was a size 11 & sent 3 photos which clearly show it is NOT a size 11. See for yourself in the photo below with the huge gaps which were the same gap on my fiance's ring finger.
My fiancee Paul rang up Greg & said look at the photos-clearly not size 11. He agreed it did not look like a size 11 but then we had an email saying,
' The "gap" was due to the type of mandrel used - it is concaved in that area to protect an exposed culets when sizing "diamond" rings. Being that our Quality Control department has verified, to our satisfaction, that the ring is size 11'
Basically they are refusing to admit the ring is not a size 11 & say we can resize it but will have to pay the shipping charge OR they will refund in full-but we loved the ring & they just need to admit their mistake. But what is the point of resizing it to 10 3/4 if they claim that is a size 11?
Really unhappy with this-we are getting married in a month tomorrow!
Thanks