Our rep from a Huge Peripherals and Equipment supplier liked doing final closures on the phone (That's the bit where they pile on the very expensive extra stuff onto a basic proposal that you had already discussed with them in previous meetings, and send you a "final contract" to approve). His technique was to go silent on a sticking point - The theory was that you (the punter) would fill the silence by agreeing the extras. It took me a couple of calls before I realised what he was doing, so I started doing the silent treatment back to him. My best call was after about 30 seconds of silence when his nerve cracked and I heard "Hello, Hello!, HELLO!!". I apologized and said. "Sorry, I had to cover the mouthpiece - My colleague wondered if I could take an urgent call on the other line from Some Unbelievably Nice supplier, as he thought I was on hold". After that his phone calls were just to arrange meetings, or "courtesy calls" to check that the kit had been delivered and installed.