Entering Phone Lists | Technical service details | Consumer forum

I have a question about how to list phone numbers under "Contacts" in order to use the direct dial option. I always list the area code along with the phone number, and include the prefix "1" for calls that are outside of my local calling area - since this is how I would naturally dial the phone number to make a call. But what does the "+" that precedes the "1" prefix mean that I found entered on my phone. For example - "+1647xxxxxxx" is listed as my voice mail access number. Is this "+" necessary in order to activate the direct dial option? Or was it entered in error (by whom I do not know)? I'd rather not waste costly air-time by experimenting with this. Thanks for your help. Cathy M.