Random small charges to my account

Earlier this month I spotted a £3.33 charge that had been made to my card for a hairdressers' I've never visited. I froze my card and reported this to Monzo.

It's been weeks and I haven't heard anything from Monzo. The charge from the hairdressers' has now disappeared but has been replaced with a charge (from around the same time) of exactly the same amount (£3.33), this time from a beer & wine shop I've never visited. What is going on?

Is this a glitch in their system?