I'm not sure if any state has any weird law about what your talking about; But I am very confident that there is absolutely no requirement for anyone to answer a phone or door. I'm sure there are circumstances regarding your front door, but I don't think there is a requirement. If they have a warrant, or think they can get one later, they will just bust your door down. As for the vaccine checkers, your best legal bet is to post both: a no trespassing, and a no solicitors sign at your door. Also post them on any conceivable entrance to your property along any of your property within 200 yards of the physical home. They would be trespassing if they violate those signs, which you could push for charges on. More importantly, if you are in a castle law state, you may be legally entitled to draw a weapon, and/or take physical action to remove the trespasser. I would consult your local laws on the matter before hand. Plus, if they damage anything entering the property, you can sue their ass. Stepping on gates causes them to droop, damaging them, and possible requiring a replacement.