To ask for help re Ebay buyer saying item wasn’t in envelope

[Rainraincloud]

What do I do here? Item was sent signed for with Royal Mail. Buyer sent me photos with the envelope looking like it had been cut open.
I don’t believe the buyer and will contact Ebay.
Buyer messaged asking for a refund.
Any advice apart from speaking to Ebay?
Thanks

Thanks!

Why are you so deadset on blocking them? It doesn't sound like they've done anything wrong. Not that they're necessarily going to buy from you again of course