Hi, I recently had to change my cell phone number due to a psycho wanting to misuse the information and "find" me. He contacted a company to try and trace the source of my internet use and other ridiculous stuff. With my number, I didn't close the account, I just called and asked them to change my number, which they did...

Since changing my phone number, I've received a few "unknown" caller Ids and typically don't answer them; a message is never left. Today however, I picked up because I was expecting a phone call from a doctor and not sure if it would come up as unknown or not. As soon as I picked up, I could hear someone sharply take in a breath of air and then be quiet. This went on for at least 30 seconds, with both of us just listening. Finally the person disconnected. An hour and a half later, I got another unknown call and did not pick up--no message left. I have a feeling it was him, but how would he know my new number?

Is it possible for the psycho to have found out my new cell number? His best friend works in telecommunications, although not for my service provider...

Hey snap, I've been going through this recently too. I called my service provider, and they have a log of the call but for legal reasons cannot give it out.
You should go to the police and report it. I didn't bother, in my case it was only a couple of text messages,so I had a number, just not a name. I called the number from a call shop and texted from a friends phone "who is this?" I haven't heard from the guy since (he answered when I called him)
The police take this kind of thing seriously. And they can access his/her phone and charge the person. Alternatively, if YOU know anyone in a telecommunications company, get them to run a check on your phone - but it will have to be done discreetly. People working for phone networks lose their jobs for doing things like that.
Also be sure your number isn't advertently on the net. Google yourself. Are you in a public sort of job? Is your number available to people in your profession? Just in case it might be someone else. You never know. Check your msn account, things like that to be sure your number isn't in your profile. Or that white pages thing in msn.
I hope you get it stopped. Good luck.