Most offices that have more than one telephone line can combine the lines using a phone company feature called Call Hunt. If you have 4 lines and line 1 is busy any incoming calls will roll over to lines 2, 3, and 4.

In order to determine which number need to be forwarded you should only consider the telephone number you give out to the public.  In most cases this will be line 1. Keep in mind that when you activate call forwarding on your primary line call hunt will be disabled.  All calls to your primary number will be forwarded; no calls will roll over to the other lines.

Your answering service and selected contacts can reach you if you are in the office by dialing the telephone number for line 2, also referred to as a private or back line.

If you have more than 1 number that you give out you’ll need to call forward each of those numbers independently.  The exception to this rule is toll free numbers as they are normally piggy backed onto your primary line.