Yes, iwantoutnow, why pay the postage. Just say you mailed them.
I used to check out a phone territory, call the first #, if no one answered I would jot it down. Then if no one answered after the 2nd time, I would always call that number and start checking how much time had gone by and then call it again. I did other things between the first call and the last call.
I know jws that did that with calling back on people. Called at a time they knew they would not be home, to start counting time. Did other things then, shopping, errands, cook at home, etc. Then on the way home stopped at that same place (near their home).
I knew older jws that called on people we called 3 hour cookie and tea stops. These jws had been stopping by to see these people every week for years. Never dropped them despite WTS "suggestions" that they do so.