OK, I'll hold my hands up to being caught by these people and so I thought I'd share my experience. Coincidentally, I was having problems with my PC and got talked into 'signing up' for the gold service that would improve the speed of the computer. Once I'd pressed certain keys, the 'Microsoft' guy took over my keyboard and I could see my cursor performing all sorts of actions including emails expressing satisfaction with what I had bought (for around £120 if I recall, on my credit card).
Upshot was that my PC became completely unusable and couldn't even access my own documents. I phoned the helpline number (a London code which I guess gets transferred elsewhere) to get it sorted and each time I was told to switch on the PC and they would sort it out. I said no chance and I simply wanted my money back.
In the end, my son sorted it all out by reinstalling everything and the PC has since worked fine.
There was a happy ending in that I got the refund via my credit card company - which surprised me greatly given that I'd willingly given my card details to what in hindsight was clearly a scam.
For a number of weeks after I was pestered with 'phone calls from these people saying that they wished to reimburse me and 'so sir, if you'd just like to go to your computer and switch it on.........' Well you can guess the rest.
I have to say I never thought I'd ever get caught out by this sort of thing and just goes to show what can happen if you get caught off guard.