It's definitely not easy for those of us running an operation with just one or two people and a significant, national demand for custom work. But multiple attempts at contact being ignored for weeks really isn't excusable. Sometimes things slip through the cracks, but it's just not that difficult to at least mark an email unread or write down the details from a voicemail. You just have to come up with an efficient system to keep track of it so you can get back to people at your first reasonable opportunity. And most folks are OK with delays in communications, as long as you do communicate. With us, for example, Jerrica handles 90% of our communications and will get back to people within a day. Some of the highly technical inquiries, though, she'll have to do just a greeting of sorts and then mark it for me to deal with later, which may take a few days.
We get 25-30 calls & messages each day, which is not huge volume, but it's significant for small operations. We occasionally drop the ball, I'd say maybe one in a couple hundred conversations goes cold on our end because we just plain forgot. But we never ignore people, so a follow up contact from the customer will revive the discourse, with an apology for our failure.