I'm alwaus very nice to them, but I also firmly explain that I'll search for anything I want all by myself.
Last caller asked if I lived in an appointment or a house (selling ev panels or heating or something I guess), I switched around and asked how he lived, after a confused but correct answer (he lived in an apartment) I asked him where he lived, mini hilarity ensued. I wished him a good day and courage because its probably not the funniest job, I think he got a small genuine happy happy, or so his voice sounded.
Have got zero calls since.