How to post a review of a bad service in a legal way?

Dear Sir/Madam,

I asked a veterinary clinic to tell me what the names of the last medications I paid for were. The vet had handed them to me in a rush and never billed me, and I had come in on my own to pay.

The receipt for which I thought the payment was turned out to be for something completely different. The vet has no notes on the matter. Same with the manager who took the payment.

I have asked them to check the CCTV as I remember the date and time, but no answer. I don’t know if this is illegal!

If I mention this incident in a review, could there be legal repercussions for me?