EBay recently made the Resolution Centre where we can open Disputes both easier to find and harder to find.
It's at the bottom of this page-- quite near the Community link that you did find.
http://resolutioncenter.ebay.ca/
It used to be under Help and Contact at the top of the page, but that now leads to the endless loop you complain about.
However.
You did the first step by contacting the seller.
She asked you to return the unsatisfactory item and when she got it back she refunded you.
You have interpreted the refund as the selling price plus your return shipping. Was this more or less than the original amount you paid for shipping?
If you had gone through the Resolution Centre, you would have been required to use a tracked/delivery confirmed service. This is more expensive than untracked services.
If you had gone through the Resolution Centre, you would have been refunded your original payment, the selling price plus shipping, and no more.
So as it stands, both you and the seller are out a shipping cost. You have your original purchase price back and she has her item.
You could go to the Resolution Centre and try for more money, but.... look at 17 cents a minute (the ON minimum wage) how much time are you willing to invest in getting it back? And probably not winning the dispute.
If you purchased through the Global Shipping Program, oh lordie lordie, this would get sooooo complicated, since the seller would not normally be involved at all. Again. Seventeen cents a minute.
