Noted that you have exchanged messages and your buyer is claiming that he has sent you photographs that you have not received.
I assume he has not said that box was open or anything similar and at this stage we must not jump to conclusions as it is always possible that item was scratched during production/ assembly or some substance has gone on during packing that looks like a scratch.
In my experience there is little value when and if you receive these photographs but asking for these is important as less experienced fraudsters may get scared and stop.
If and when your buyer opens a return and reason stated is Not as described or damaged I am sure you already know that you have no option other than to accept a return and a pre paid label will be offered by eBay (At your cost) or you provide a label and hope that item returned is yours and as you fear not a switch.
if item is switched as you fear then I am sorry to state the obvious but refund must be issued and you can report the buyer as abusive on eBay.
I don't expect eBay to do anything as they never have sight of what sellers send or buyers return.
As for Pay Pal I can not see them doing anything even if your buyer makes a charge back claim as all they will do is ask the buyer to return the item via tracked& signed service and when tracking shows item is delivered then they will issue a refund to buyer and debit your account. Pay pal take the same view as eBay that they did not have sight of what you sent and what buyer returned.
Noted that you have "images of the box so have imei and serial number so could in theory get a phone shop to check once they are open"
In the event that you become the latest victim of online crime then only option available to you is to file a crime report with your local police station as this is a growth area and most police stations have a dedicated team to deal with this crime. No doubt police are underfunded and under staffed to deal with such a heavy workload but you never know they might just go and knock on your buyers door and if phone is in his possession then you would have had a result and he would have a criminal record.
at this stage I would just sit tight and I would respond to all of buyers messages but as briefly as possible and I would not get involved in an argument. If he asks for a partial refund then my advice would be to agree to this amount and tell him that as per eBay's policy he must open an INR case and you can refund through this case.
Tactically this protects you from buyer opening another case and as you haver already agreed the amount then on the case itself you have an option to offer a partial refund which buyer accepts and case closes immediately with buyer getting the agreed amount and Pay pal is notified that a partial refund has been agreed and he will now have great difficulty in opening an item not as described case on Pay pal.
My apology for such a big post but I wanted to cover as many eventualities as possible.
Let us hope it doesn't turn out to be complicated.
