[fxtentacle]

You should also assume that your employer can take those things away instantly.

For example, one day your laptop forcibly restarts and afterwards you're locked out. Then a day later, you get the call that you were canned.

So always keep private communication separate and get private phone numbers / email addresses from coworkers that you get along well with. The company can delete your extension and email address, but with a bit of preparation that doesn't have to be the end of your personal relationships.