Time slots a waste if not going to follow it!

I ordered and chose a delivery time slot of between 15:00 and 16:00 as I was going to be in a meeting until 15:00. While I the meeting a saw someone call 14:44 but I couldn't answer. It was the delivery person and they had left when I was done at 15:00 as they only wait 10 minutes. What was the use of selecting a time slot if they don't follow it. I got a credit on the app, but the delivery fee was not credited. It was not my fault, so why is the delivery fee not credited. Would never use again.