Case opened via buyers financial Institution

[purelyplaques]

Im hoping someone may be able to help me. Over the last week I have had two cases opened for the reason "transaction not recognised" Ive been advised by ebay that the buyers have gone straight to their financial institue to claim their money back. Neither buyers have contacted me via ebay to advise of any issues. First case this week I contacted the buyer. They claimed they hadnt opened any cases and that they apparently only tried to message me the day before. Ive received no message from this person. I then informed them that ebay had told me that they had opened a case up via their bank, When I questioned the buyer about this i have had no response 😞 2nd Case 2 days later, same reason, didnt recognise the transaction, Emailed the buyer to ask if anything ws wrong as tracking showed delivered and they came straight back to say yes all received perfectly however they had opened a case for another person but it seems its opened it up for other sellers too. Found this very strange as she had gone through her bank too. When I replied and asked if she'd opened it up with her bank and could she close it as this has been opened incorrectly, no repsonse. Sent an additional email and no reply to that either. What I also find strange is that both cases are from the same area and live 1 mile away from each other. I provided tracking to the case and have emails stating she has her item and still I have lost the case, lost my money and been charged £14 dispute fee!!! Contacted ebay and they are now challenging this case however Im not holding my breath as they told me they cant give me 100% guarentee that even with the tracking and an email to say the buyer had received it I still may not get my money back!! Has anyone else had anything similar happen to them? I find it strange that in a matter of a couple of days Ive had two of these cases opened and ebay claim they have been opened outside ebay which I dont believe at all. If anyone can give me any help as to how these cases are actually opened or if this is some sort of new scam I would be greatful 🙂 

[plpmr]

now there's two kinds of unauthorised use cases -

with eBay you have to prove that the item was delivered to the address eBay gave you on their payment advice.

with PayPal you have to prove you posted the item to the address PayPal gave you on their payment advice.