I once had a similar experience with Amex. The ‘proof’ was a charge receipt with not my name, not my address, and not my account number from a location I had not been in years, and demonstrably not when the bogus charge was made.
It was obviously a database corruption in their system rare as they may be even in the 1980’s, and both my account and the other persons account got linked as ‘me’. It took months to work through their incompetence.
Excepting while Westpac issued ‘Westpac Amex companion cards’ with their Visas, I never accepted an Amex again, not for business nor pleasure. One rarely forgets or forgives such gross incompetence at the obvious.
