could be as simple as not being logged into trademe or attempting to answer when your listing has closed,
most of my items are larger, but still ok for courier service, a few push the boundaries a bit, the 2 couriers i use are nzc and pbt , nzc will , but load the price, pbt quote 1 price and frequently invoice at different rate, so i gave up as it was always a bun fight, and frequently i never made money on the transaction. it was easier to just not send to waiheke and avoid the nonsense which is ok, i state on my listing no courier to islands, but now the auto customised trademe to the buyer shows freight to waiheke , which can excite them a bit when i say no, but their viewpoint is also cor...
that would depend on the item and service you are using
Recently, we do not ship to islands such as waiheke , this is stated on our listings, island shipping has always been problematic for us, anyway a a waiheke island buyer purchased and was a bit put out, it seems that the trademe personalised listing shows to him, waiheke and a price , which we dont do. i have not asked trademe how to opt out but doubt that i would get a useful answer, the only solution i can think of is to include a waiheke freight option at a silly price, which i am reluctant to do.