Customer has returned a used item for a refund

I recently sold an item that customer has now returned stating it had only been used a couple of times and not suitable for purpose. the fact that it was nearly a month after and the returned item has been used to the point of destruction and possibly isn’t the same one I sold doesn’t matter to Amazon as they have authorised the refund.
Is there a way of disputing Amazon’s decision? i cant find any info on how to stop my £250 pending refund for a clear case of the buyer trying to con me !!!
Any help on this will be very welcome