Approximately 6 months ago, I placed an order with a friend of a friend for laser engraved dog tags to distribute at as a keepsake at an event I attend. We agreed on a price, I provided art, and they let me know that they would send me a sample before filling the order. They also let me know that they would follow up with payment details.
After this initial conversation, I had no further contact with this individual. I never recieved the sample or the payment information, and they did not respond to my follow up emails as the date of the event approached. A few days prior to the event, to my extreme surprise, I received my complete order in the mail with no accompanying documentation. Additionally, they appeared to be screen printed rather than laser engraved. I sent another message to coordinate payment at this stage, and received no response. I did end up handing out the tags at the event, and was very pleased with how they were received by the other attendees.
After a month of no additional contact, I assumed the order had been written off as a loss, and that I would not hear from this individual or their business at any point. I was surprised today to recieve both an email, and an invoice from them asking for payment in full.
I am going to pay the invoice, as I did accept delivery of the order, and use it as intended. That said, I feel like I should say something to them about their poor business practices and my dissatisfaction with the transaction.
How should I respond to this message after I have paid the invoice?