Obviously you lose your sense of privacy when using the companies properties the day you start work at the company. As the company is the one invested in all the hardware, hence its in their best interest to see that their investment is being used in the right manner.

If a company gives you a Black Berry, pays for the bill. Hence, the company through the HR would have the right to go through the numbers of calls you made etc.

If the company provides you with a laptop/desktop and internet connectivity, they can block or record your activities.

If you're using VoIP, and the company installs a product like BlueCoat, they have the right to replay the session and listen in to what was transpired in the conversation.

Hence, if you want to do something which is not business related, then do it after the office hours and not using the companies property.