After my father died, every time I visited his house I received phone calls from a company who thought he had not made his monthly payment to them. This in spite of the fact that our solicitor had written and told the company that my father had died, the bank accounts were frozen and payment would be made in due course.
The person who phoned was aggressive and persistent. He obviously did not believe that my father had died, thinking I was making excuses to avoid paying up.
Eventually, I wrote a letter of complaint and received an apology and a small amount of compensation.
This was six years ago. It was infuriating and upsetting and I have not forgotten it. I have, however, forgotten which company it was!