I recently MoTed a car for a long time customer, he said he had sold the car to a neighbour, so I kept the cost as low as practical, no problem.
The next day (Friday) the new owner phoned and asked if I would service the car, she asked for it to be done over the weekend (strike 1) No, I don't work weekends. So I arranged it for the Monday, how much? I estimated 200 pounds total (remember I had seen the car and had a rough idea of the state of it), she was a bit incredulous (strike 2), but agreed. She wanted the car collected (which is normal for me) and we said 9.30 am after she dropped her child at school.
I got there for 9.25, no car. At 9.40 I went to the door, just in case. a child answered and said that she (the owner) would be back in 2 minutes. 10 minutes later at 9.50 still no car (strike 3) so I drove away.
A bit later a tremulous phone call, saying she suddenly had to go and post something, so was late. I accepted her apology but refused to re-book the car. She then started snivelling and arguing, saying her husband would kill her etc. etc. I eventually had to say I was hanging up now. She left another whining apology on the ansaphone later, so I blocked her from calling.
All she had to do was ring when she knew she couldn't be there on time, just common courtesy, I think.