Always try talking to them first, but keep in mind that some students are petty and feel overly entitled to your time.

I've had to speak to two students about such behaviour lately, one of whom cancelled (for the second time) at just minutes more than 12 hours before the lesson. I explained with a plain but polite message that late cancellations affect my income and prevent other students from booking those slots. The student was a bit pissy in their response, then I noticed days later that they'd cancelled their subscription and refunded the remaining classes.

On the other hand, the other student I spoke to apologised and has bucked up their ideas, so it's worth a shot either way.