You can either fret about it or have fun with them. When they call tell them your never going to pay them. "I don't pay taxes why should I pay you?" and hang up.
My favorite is answer the phone with "I don't know what to do?.....There's blood everywhere and they are not moving!" Then hang up.
Starter pistol....two shots then "Your next mothertrucker!" Hang up
Of course you have to unplug the phone or turn off the ringer after any of these.