This technique also known as Call Forward Plus allows you to forward your call even when you are not home or in the office.
Each time a call is forwarded, your phone will make one short ring. While Call Forward is on, you cannot answer incoming calls. However, you can still make outgoing calls.
To gain remote access for Call Forward, call your local access number (provided by your local telephone company). For further assistance, call 1-800-921-8101. Listen for two beep tones or voice instructions, then enter your 7- or 10-digit telephone number followed by your 4-digit PIN number. Listen for two beeps or voice instructions and enter the activation/deactivation feature code.
To change your call forward number, just repeat the above process. Call Forwarding Plus cannot be used from rotary/pulse phones. Ring Count is not changeable remotely and you get one free PIN reset. Forwarding calls to long distance numbers will incur long distance charges.