I've been doing the usual searching for a contact number for Ebay as my question is not listed and AI is useless..... A seller (car breaker) was breaking a car and had a part I needed so I contacted them and sorted a deal, they then said they would raise an invoice for me to pay, which I did, now been waiting 10 days, nothing arrived and sent them 4 messages which I've have  had no reply to.... Any advise what to do ?