Imagine this: Your car breaks down, and you don’t know what’s wrong with it. You take it to a mechanic, and drop it off. You call them two hours later, asking if they’re finished yet – tell them that it can’t take them long, because it’s clearly just a small problem and they’re professionals. They call you back 2 hours later and leave a message (you didn’t answer). They say that your alternator is kaput, and needs a replacement – can you please call back ASAP to approve the price.
You don’t call them back for 5 days.