Why is my DID calling an outside number ?

[SUSD]

3300 MXe 2-Clustered Rel 4.2 / 10.2.0.26_2  EMB-VM 6-SX200 10-ASU

So our Help Desk extension 6500 is a multiline that appears on 10 phones. It is not a prime extension.
I have a B1 line going to a key system I use for testing. So only I should be calling this B1 line. Now my B1 line rings and I answer it, wondering who is calling my test line and it's a staff member saying they called the Help Desk 6500 ?

So I've checked Call Routing of 6500, rings the ext and voicemail only. No other options in the Voicemail set. Checked call forwarding profile for every extension that 6500 appears at, nothing set. Checked Speed Dials, Ring Groups, Hunt Groups, Multi Level Auto Attendants - 6500 does not appear. Checked my phone carrier to see if 6500 has any hunting, they say nothing shows there.

I can't reproduce, but I think it depends on how many extensions have the line busy before it ends up calling my B1.

Any clues where I might look next ?   Thanks !

[ralph]

Turn on internal SMDR.  Then when it happens check the smdr record of the caller.
That may give you a clue as to what was dialed.

Keep in mind, it is possible for a user to use a feature code to forward buttons.
I don't remember if you can do a loc feature on a non-prime but give that a shot too.

Ralph