Online shopping flop!

Online shopping a flop. Placed an online order for delivery between 10am and 1pm on 4th June. No delivery takes place instead I receive an email saying the driver returned with items as I did not answer my phone. The reason I selected a specific slot is because someone was available at that time. My call history shows 3 missed calls after 1pm. Why have available slots if they not adhered to. And why call customers if they agreed to a specific time slot?