No response to 3 requests for an invoice - am I obligated to finalise with payment after 3 weeks?

[dnat42]

I purchased an item on 26/9 which clearly stated postage to Aus available. When I tried to complete checkout, I was told to contact the seller for cost/invoice. I did so immediately via eBay email.

No response. A second request 2 days later - no response. A third request 4 days later -still  nothing.

I have now left negative feedback and immediately received a response that postage was added - they were waiting for me to pay. They also stated they would like me to revise my feedback.

Two questions please-

1.  I think I have been reasonable giving the seller 3 opportunities to reply. Am I still now obligated to complete the purchase (which I am now no longer interested in doing)?

2. Am I being unreasonable by not agreeing to alter my feedback -  as this appears to be the only thing which has prompted them to reply?

I did not leave neg feedback without a great deal of thought, but I believe it was warranted. Am I wrong?

Thanks for any answers you offer.