Disclaimer: this is my first AIBU and it is trivial and I probably ABU, but please be gentle with me. 
I regularly have my shopping delivered by Sainsbury's and on the whole I am very happy with them. However, they routinely try to deliver early. They will ring me and if it's ok, I'll let them come early, if it's not I make them wait until the delivery slot time.
Today, I was at work. I had a delivery booked for between 6pm and 7pm. I got home at 5.40 and passed a delivery van, with the driver sitting there reading the paper. I got home and he had already been and delivered! He got there at 5.30 - half an hour early! We have a Nanny who was there and he told her he had phoned me!
I told her if it happens again to tell him to go away and come back at the correct time. I was annoyed because, firstly, it is not her job to take the delivery and put our shopping away, and secondly, I like to be there in case there are any odd substitutions.
Anyway, although annoyed, I wasn't going to do anything about it.
I then left the house again at 6.05pm to take DS1 to football training and passed him again in his van, still reading his paper! I wanted to stop and tell him off talk to him, but DS wouldn't let me. 
So, would IBU to e- mail and complain, when he could have sat there prior to delivering when he obviously didn't have to be at the next delivery for a while, rather than delivering half an hour early?