Morale of the story ?
I'm repeating myself (used this same topic in another alike thread) but still I think you can't stress this out enough:
Never, EVER, make (semi-) important decisions over the phone. Company calls you to provide you a better deal for your energy, (cell)phone, internet, etc. ? Never say yes; instead ask them to send you the offer in writing (heck; even an e-mail will do; how hard is that?) and only then decide for yourself if this deal really is as good as being claimed.
Same applies to this stuff. Never EVER give others who you don't trust access to your computer "because". Same issue applies here: ask them to send you the information in writing so that you can check for yourself if this is something you should be doing.
Most of all with computer issues like these: Ask a friend who knows about computers FIRST !
I know most of you will now go "Yawn, dude... we KNOW all this....".
Sure, but do your friends and family also know? Do your neighbors know? Does that friendly old chap down the street (or 2 floors below) who's walking his dog know ?
Those are the guys to look out for, those are the guys where you should bring up subjects like this (if applicable and when possible of course) and warn them about such issues.