As I often tell people, ordinary people have the luxury of ignoring your emails, phone calls, etc. People who work with the public, simply don't. It's rude. It's wrong. No matter what your reasons might be.
As hard as it may be to believe, once upon a time there was no email, texts, or voicemail (or even answering machines). If someone called and you didn't answer, without getting their knickers in a wad they simply assumed that you were out, and would call again another time. The notion that the rest of the world should be constantly at your beck and call would've been thought perfectly ludicrous.
It goes back to the old thing of not shooting the messenger. He was not the one who made the mistake that you are complaining about, or sent you the wrong size shoes that make you look like a clown.
When a guy told me that I did not respond to his text message, I simply told him that I never read those things, because 98% of them are spam. When I showed him my phone that showed "285 unread messages" (over about 4 years), he was a bit lost for words. During that period, since I changed to the phone, I have sent 3 text messages. LOL
