poor customer service - YET AGAIN !!

why do you even bother adding a delivery time if you are never able to meet your commitments? I placed an order last night at 20:25 with delivery promised to be between 07:30 and 08:00. it is now 08:00 and the order has not even left the store yet, and surprise surprise, the delivery tim is simply updated to now be between 08:00 adn 08:30. I then phoned the call center to enquire as to why they are never able to deliver my orders in the time stated, and the agent named Faith simply hang up the phone while I was speaking. Surely this is unacceptable???