Turn off voicemail 6408D+

Change number of rings before voicemail answers

Go to Account overview > My digital phone > Check or manage voicemail & features.On the Voicemail Settings tab, scroll to General Preferences and select Set Number Of Rings Before Voicemail.Choose a setting ranging from 1 ring (6 seconds) to 6 rings (36 seconds).Select Save.

Turn your voicemail off ? thru setttings then call.? or try this
type this into your phone
**61*101**30#
press call
this will extend the ringtime from the default of 15 seconds to 30 seconds
Change How Long Your Phone Rings Before Sending Calls to Voicemail

The KX-TG2313 isn't an answering machine. It will ring until you pick up, an answering machine or voicemail system picks up, or the caller hangs up.

To change the ring count, refer to the documentation for whatever answering machine or voicemail system you have on your phone line. If you require further assistance, please add a comment to this question and identify the answering machine or voicemail system.

The CS6419 isn't an answering machine. The phone will ring until you answer, an answering machine or voicemail system picks up, or the caller hangs up.

To change the ring count on an answering machine or voicemail system, refer to the documentation for that system. If you require further assistance, please add a comment to this question and identify the answering machine or voicemail system.

The TRU9466 isn't an answering machine. The number of rings is controlled by whatever answering machine or voicemail system you have on your phone line. Please refer to the documentation for the answering machine or voicemail system to change the ring count.

If you need further assistance, please reply to this post and specify the answering machine or voicemail system.

I don't think it's possible through the phone software, it may be something you will have to do through your network service provider - if you log in to your account online there MAY be settings that can change the number of rings before voicemail picks up, or call the ever-reliable customer service...

The 6041 isn't an answering machine. It will ring until you pick up, an answering machine or voicemail system picks up, or the caller hangs up.

Please refer to the documentation for whatever answering machine or voicemail system you have on your phone line. If you require further assistance, please add a comment to this question and specify the answering machine or voicemail system.

For all of you that want a real answer here ya go. This isn't something you can change on your phone this has to be changed with your service provider. If you are with AT&T, like I am, then this is the solution for you (link of where I found it below as well). 1. enter *#61*11# and press send/talk on your phone.
2. write down the number your calls are currently forwarded to (usually +1401#######, but not always). this is your voicemail deposit number.
3. decide how long you want the phone to ring in 5 second intervals. the maximum time is 30 seconds. i'd recommend 25 seconds or less, as using 30 may cause you to be billed for a minute of airtime each time someone is forwarded to voicemail.
4. now enter **61*[number from step 2]*11*[number from step 3, use 2 digits]# and press send/talk.

example
voicemail deposit number is +14015551212
you want it to ring for 20 seconds
you would enter **61*+14015551212*11*20# and press send/talk.

if you have trouble with the above procedure, you can always call customer care at 800-331-0500 to change it.
OR QUESTION: How can I adjust the number of times my wireless phone will ring before the caller goes to voicemail? ANSWER: Contact Customer Care at 1-800-331-0500 or dial 611 from your wireless phone to change the amount of time your phone will ring before going to voice mail. The adjustments made by Customer Care are based on the traditional ring heard by the caller, not the unique Ringtone you hear from your phone. I just wanted to add that increasing the ring length to 30 seconds will not cause you to be charged a minute should the caller go to voicemail. This was confirmed by an AT&T technician.
http://forums.att.com/t5/Voice-Mail/Increase-the-number-of-rings-before-a-call-goes-to-the-voicemail/td-p/2576651

This happens when the number of rings to answer of the provider voicemail is less than the number of rings to answer that the answer machine is set for. For example: if your provider voicemail rings to answer is set for 3 rings and the answer machine is set for 4 rings then the voicemail answers before the 4th ring, therefore the answer machine will never get a message. I would call the service provider's customer service number and request they increase the rings to answer above the number of rings to answer that the answer machine is set for. If you don't want voicemail to answer any calls(when your line is busy or when the answer machine is turned off) ask your service provider to disable voicemail.

Sounds like you have either send all calls (SAC) enabled or your station is call forwarded to voicemail.

Disabling send all calls or call forward (as applicable) will solve the problem.