I have two lines and it is my experience that I can receive
a call on either line without changing anything.

Now, if you want to make a call from line 2, you need
to switch to it.

Here is the scoop on Alternate Line Service (ALS) on Nextel. When receiving
incoming calls, your unit should indicate which line is receiving a call and
ask if you want to take the call. To answer, you simply choose "yes" to take
the call, or press the "send" (the one with the green phone) button. To have
the call go to Voicemail (VMS) simply do nothing or press "no". The ALS line
cannot have it's own VMS, it needs to share VMS with Line 1. So if you have
a phone issued by your company and they pay for line 1, the plan they chose
for Line 1 either needs to have VMS inluded, or the company needs to fork
out a buck a month for VMS. If this is your case and the company doesn't opt
for VMS, you will be S.O.L. when it comes to VMS. Even if you call Cust Care
and have them add VMS to the ALS (which unfortunately you may get someone
who is new and may not recognize this unless you tell them it is an
alternate line) it will not work.

Example: Line 1=360-555-1212, Line 2=360-555-1213. Line 1 has VMS, so the
number the calls get forwarded to is 360-555-6245 (6245=M-A-I-L on your
phone keypad). Someone calls line 2, you don't answer, the call gets
forwarded to 360-555-6245, or Line 1 VMS. If you do have VMS and an ALS, I
suggest you make sure the greeting is recorded or at least you have recorded
your name. Since calls for both lines go to the same VMS box, if you elected
to just keep the default automated greeting, callers for line 2 may get
confused. When they get the VMS it will say "You have reached the voicemail
for 360-555-1212, at the tone please leave your message", and they are
calling for 360-555-1213.

As for forwarding, the only number you can forward your calls to without
charges is the ACFN (automatic call forwarding number, or VMS box). All
other numbers will be charged at 20 cents per minute for airtime (current
rate for forwarding, which may change in the future, but will specify on
your bill in the NEWS section, and on Nextel.com if it does).

Another piece of info, the ALS will also require it's own rate plan. But on
the plus side, ALS does not require a Commitment (Service Agreement,
Contract, whatever your choice of words), because Line 1 is where
commitments are bound to.
Current ALS plans can be found at
http://www.nextel.com/services/digitalcellular/alternatelineservice.shtml

Hope this helps a bit.