Not only the elders, but the women in the congregation used to do it to me. I worked shift work, had young babies, and asked repeatedly for them to call first. The most that ever happened is that they sat in my driveway calling me on their cell phone when I wouldn't answer the door.
I wasn't raised in the religion, and I never had that problem until I met this particular group of people. They always thought I was being too touchy as I honestly became furious at the intrusion. Hey, either I was sleeping during the day after working all night, or one of the babies had just laid down, and there was hardly any time for making the house "company ready".
Actually, I've often thought this was done on purpose as it seemed to give the JW women a reason to feel superior that their house was perfect. I really could feel the smugness roll off them.
As for asking the elders to call first, I did repeatedly. Never happened. So we put the No Trespassing sign up. I was tired of feeling like a prisoner in my own home.