I have taken to winding them up something chronic. I even offer to send them (none existant) photos of the insides of my leg before it was stitched up.... they have finally started to leave me alone now and don't get those calls anymore! I only have the photos of afterwards - which was an oversight on my behalf and it would have proved more useful once back in the UK if I had taken the photos before hand (I was actually given this option, but decided against it!)
 
My mother whose IT skills are legendary also has some great lines... the PC ones are the best with my mother: windows? no I've just had new double glazing all round.. 

 (I have heard her say this to them on the phone).
 
And when they ring up for loft insulation, my step-father (a retired firearms CPS solicitor) launches off into how the asbetos or the fibre glass in the insulation ruins his firearms in the loft and he has to get them all down again to clean them and it takes him so long to get all 59 of them down, clean and back up there... (the fact that they have to be in special cases in the roof, bolted to the rafters (as well as the specially laid floor) is completely beside the point...) not to mention his questioning them about how well black powder mixes with said insulation... (he has done really old firearms. Moving house with them was 'interesting' to say the least!