I am including a link to the Blackberry knowledgebase article on using Smart Dialing for your reference. BlackBerry Smart Dialing
The Blackberry is good, but it is not smart enough to know what the correct area code is when you manually
dial a number. If the phone number is a 7 digit number in your phone book or link in a message, it will add the Smart Dialing Area Code you specified. Otherwise, it wants you to specify what area code you are calling. In the Toronto-GTA we have a total of four area codes that may apply so you need to be careful how you use this option. I have found it easier to just put the appropriate area code with each number (all 10 digits) in the phone list or manual dial and I leave the Smart Dialing Area Code blank.