I have a relative who has never heard of a two sided conversation. I have to periodically call her and always dread it. If I can manage to get a word or two in she starts loudly sighing in the background to indicate that she is not interested in what I have to say, and then just interrupts and goes back to her constant drone.
I have tried everything from talking over her, to saying, "if I can just say this". Nothing works. She wonders why no one wants to call her or invite her to anything, or if they do, everyone runs for cover if she comes over. One relative plucked up the courage once to call her a "conversational terrorist", but it didn't seem to have any affect.
If anyone finds a cure, let me know.