Just hang up...sorted.
I you feel up to it, I say keep them talking. The time spent talking to you is time unavailable for scamming somebody else. I do it all the time, even with the more innocent marketing calls.
Tell them to hang on while you answer the door, or tell them the need to talk to some mythical person who's upstairs and will be down in a moment. Every few minutes, pick up the phone an reassure them they won't have to wait much longer.... In fact, I have a lady with a lovely Indian accent hanging on right now, even as I type. Ah the joys of summer.
