postage question

[kyles278]

I have a question I would like some assistance on. My ebay account automatically defaults details to the United Kingdom as that's where I normally live, but am out here in Australia for a few months. I recently won an auction for an item on ebay.com.au and when this happens, i straight away email the seller clarifying my australian address and making sure the postage is correct. I had only recently thought to do this after realising that some items when i click to pay by paypal it automatically pays without allowing me to change the address. I won and paid for the item, only after did i relise the postage charge was set on international rate of $17.95 instead of the australian rate of $8.50. I wondered that perhaps the $17.95 was the correct rate for domestic post, so I checked the postage on the item when it arrived, which was around $6.00. I contacted the seller immediately stating what had happened and requesting a refund for the postage difference between $17.95 and $8.50. They have failed to contact me after I have contacted them several times. I have just attempted to open a dispute due to this but am unable to for the correct reason. Am I being unreasonable in expecting the seller to refund the difference in postage? and if not, what options are available. Thank-you