When a seller is not helpful, you have to stop communicating with them and open a case for INAD (you have 30 days since the last day of the estimated delivery on eBay and 180 days since the purchase in PayPal, if you used it to pay).

It is useless to try to communicate with sellers who are not willing to help and if you wait too long you won't be able to open an eBay case any more.

PS: You are not allowed to name and shame, as it is against the rules of the forum.