If it's a cell phone, you needn't add the area code. But if you call a fixed phone, you should dial the area code. (usually the fixed telephone numbers in China are formed by seven or eight numbers, while the cell phone numbers include eleven numbers).

Mrs Lee, thank you for your reply. The number I am trying to call is 020 8543**** (I will leave the last 4 numbers blank for privacy) I am dialing from Canada, so I am dialing the 86 for the China country code. So should I be dialing this 011 86 8543****?

Thank you for your help.