Here is the thing I have a business as well and have been involved in customer service for a long time. "acknowledgment" doesn't have to be a phone call it can be a 1-second email or text with 1 letter "K" that's what has become acceptable today with technology.
Prime example.
I sent a return email to your sales rep after getting the quote and I noticed she had the wrong investors, not the ones I wanted. I wrote back asking for them to be changed. This was on September 30th. I realize that was a Sunday. On Monday if I had received an email that said just the letter K I would have felt like I was being taken care of. By Tues I probably should have received the quote back or if the rep was not working Monday maybe I would have gotten the K email. I had to email her back on Oct 3rd asking if she got it and still did not get any response. When I finally got a hold of the rep I think it was by phone the explanation was I changed your quote already I'm just waiting for shipping costs. All this time I was in the dark though frustrated.
I had the same problem with the other rep and this leads me to believe the issues I'm seeing from others' frustrations. If I have a problem with a piece of equipment am I going to get a response to a question or inquiry every 5 days only?