I have an NEC Model DLV(XD)Z-Y(BK) DT300 series phone that goes straight to voice mail. I have tried canceling DND and Call forwarding. I don't know if these features were even enabled.

Cancel DND or CALL FORWARD ALL. On an Elite, SPEAKER 42 is cancel code for both, or Feature 60 just cancels DND.

Your phone is either on Do-Not-Disturb, or it is Call-Forward-All straight to voicemail. Speaker, 42 cancels DND and CFA on an IPK, an Elite, and on a Pro II if your codes are at default. If you have a newer system you might be able to scroll through the options in the display window to cancel.

Not too clear on what's happening. Maybe the phone is set to call forward all. Usually CFA code is 41 plus ext. If the user happened to dial 41......, but forgot to dial 9 first for an outside line the phone could be forwarded to the twilight zone. In this case, dial 42 to cancel CFA, problem solved. If do not disturb in on, code 40 is the cancel code. This depends on your codes being at default, if your office codes were changed, say to make room for 400 series extensions, then who knows what will set and cancel CFA or DND. If you want the phone to ring instead of voice announce on internal calls, I'll have look for that later. I know it can be done in programming, but there's probably a code so you can do it yourself.

I am not sure which country you are in, but in Australia your divert depends on your phone carrier not your model. If your carrier and call plan supports call forward you just dial their set number and follow the prompts to turn on or off.

What model of NEC phone system do you have? Go look in the phone or data room and look at the PBX. You might also be able to press Feature 3 to get some information which would be helpful to a tech. If it is an SV8100 try this:

To set the system Time:

1. Press

Speaker.

2. Dial

728.

3. Dial two digits for the hour (24 hour clock, 13 = 1:00 PM).

4. Dial two digits for the minutes (00~59).
5. Press

Speaker to hang up.

http://www.scribd.com/doc/52001638/End-User-Guide-for-NEC-DLV-XD

menu has option to do that

All forwarding can be cancelled by dialling 600, (with your handset down) you then need to re-enter a forwarding to transfer calls to your Voice Mail. Please kake a minute to look at the video I have uploaded for you, hopefully this will help you. There are more like this which include Voice Mail admin on YouTube search 'abbeytel'. or visit www.abbeytelecom.com.
I hope that this is of some use to you

Feature 69 feature.