i do that when ppl phone up from other companies trying to change my phone,gas,electric etc. My cpn has given me a role to play out i answer and before their spill i say i am happy with my current supply no thanks and before they say another i'm to put the phone down.
and if they come to my door which i hope will stop me loads of different suppliers charging me i dont know if this helps you need to find a stopping stragie (ops sorry cant spell it) if you like you can bounce ideas off of us good luck xxx