Like many people, I don't wish to receive unsolicited phone calls/texts/emails from people who are trying to sell me something or scam me.
I am aware of passive ways of dealing with the problem but I am asking here for ideas for actively discouraging such calls.
I want to discourage the same people from calling me twice.
I want to discourage them from calling other people. In other words I want to stop cold-calling altogether. I believe it has no useful place in the modern world.
I am looking for novel ways of causing the maximum inconvenience and expense to these annoying people. Of course I am only interested in law-abiding methods.
If possible I would like the methods to be scaleable to the status of a campaign.
To repeat, I'm aware of passive solutions but I want ideas for active solutions that will hit these people hardest and preferably in their wallets.
I'm very grateful for the answers so far. However they are very low-level solutions. I realise I wasn't clear enough. It is easy enough to annoy the grunts on the front line and anyway they are used to it. I am looking for ways to inconvenience the decision makers at the highest possible level.