When we were in college, my sister's cat was having trouble keeping food down. We went to the local vet there, and my sister asked for an x-ray or an MRI, but the vet's office wouldn't do it, because it was "too expensive", even though my sister had the money and was more than willing to pay. They gave her some antibiotics, but she couldn't keep those down either. We wound up driving to our family vet three hours away, who did the MRI and determined that she had a congenital defect that had caused her esophagus to twist, and she needed immediate surgery. Unfortunately, she was so weak, the cat didn't survive the surgery (though, she likely would have, if the first vet had done the MRI when we requested it, and we had proceeded immediately with the surgery).
Cut to a month later; we've notified the first vet that the cat died as a result of their negligence, settled the final bill, and found a new local vet for my cat. The local vet somehow hadn't taken us out of their database, and sent a postcard letting us know it was time for Delaney's vaccinations. I came home from school and found my sister in tears, called the vet, and firmly but politely explained to them that the cat had passed away. They apologized and promised to update the database.
Another month passes. We get another postcard. I intercept it and call them AGAIN, this time asking for the office manager. They apologize again and promise it will be taken care of.
ANOTHER month passes. My sister comes back from the mailbox in tears. They've sent ANOTHER postcard, this one chastising my sister for her cat being three months overdue on her shots.
I pride myself on being level-headed, but I snapped. I got in my car, drove to the vet's office, and asked to speak to the manager again. I show her the postcard, and explain that this is the third time I've had to deal with this, and my poor sister is hysterical, as she still blames herself for not pushing harder for the MRI that might have saved her cat. The woman rolled her eyes at me, and said, "These things take time. It was an honest mistake. Your sister needs to toughen up a little."
I went out to the full waiting room and said, "Attention everyone. Just so you know, the people at this clinic killed my sister's cat, and they refuse to take us off their mailing list. Do with that information what you will." I turned back to the office manager and said, "I will come back and tell everyone this every time I get a postcard from you. Understand?"
On the plus side, we never got another postcard from them.