Thought I should share this. On checking my Amex account on-line, I noticed that a transaction for Costa coffee had been applied twice. The transaction was contactless via Google Pay, and nothing untoward happened at the time of the transaction. Both transactions have the same date but different reference numbers. Google Pay app shows just one transaction, so may be a Costa processing problem?
I disputed one of the transactions on-line (took 20 seconds) and Amex will refund pending investigation. Nice work, Amex!