Caller : hello!  I'm calling from [public service directory name] ... we supply information for organisations in the public sector to buy from, including... 

Me : Sorry, not interested. 

Caller: Don't you do any work for the public sector?

Me : Yes, I have, it was awful, I don't ever want to do it again.

Caller:  Oh. 

Me: Goodbye. 

I regret that I didn't add ' And there are better places for them to be spending than on pointless web projects*'.

* which is not to say that ALL public sector web projects are pointless, but on past experience, any that I am asked to quote for almost certainly will be.