How do I stop Vetech cs6429-3 indicating voicemail wrongly.

Question edited for clarity.

This phone system has two features.

Answerphone system which records messages to the unit.
and
Voice Mail System which is an extended (often paid) service from your telephone provider.

Sometimes a glitch at the Telcom will remove your Voice Mail. You will need to phone their customer service number and ask why they stopped the service you previously enjoyed? They will be able to put it back in place.

Page 32 refers

https://cdn-media.vtechphones.com/products/CS/CS6929/CS6929-X_WEBCIB_V3_20160224.pdf

Retrieve voicemail from telephone service Voicemail is a feature available from most telephone service providers. It may be included with your telephone service, or may be optional. Fees may apply.

Retrieve voicemail When you received a voicemail, the handset displays New voicemail and . To retrieve, you typically dial an access number provided by your telephone service provider, and then enter a security code. Contact your telephone service provider for instructions on how to configure the voicemail settings and listen to messages. NOTE After you have listened to all new voicemail messages, the indicators on the handset turn off automatically.

Set your voicemail number You can save your access number on each handset for easy access to your voicemail. After you saved the voicemail number, you can press and hold to retrieve voicemail. Press MENU when the handset is not in use. Press or to choose Settings, and then press SELECT. Press or to choose Voicemail #, and then press SELECT. Use the dialing keys to enter the voicemail number (up to 30 digits). Press SELECT to save. You hear a confirmation tone. • 1. 2. 3. 4. 5. 33

Turn off the new voicemail indicators If you have retrieved your voicemail while away from home, and the handset still displays the new voicemail indicators, use this feature to turn off the indicators. NOTE This feature turns off the indicators only, it does not delete your voicemail messages. Press MENU when the handset is not in use. Press or to choose Settings, and then press SELECT. Press or to choose Clr voicemail, and then press SELECT. You hear a confirmation tone.

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To remove the voicemail indicator and stop the flashing light on your Panasonic home phone, you can try the following steps:
1. Access the voicemail system: Dial your home phone number from your Panasonic phone or another phone and let it ring until it goes to voicemail. Enter your voicemail password or follow the prompts to access your voicemail messages.
2. Listen to and delete all voicemail messages: Check your voicemail inbox for any new or saved messages. Listen to each message and follow the instructions to delete them. Ensure that your voicemail box is empty.
3. Exit the voicemail system: Once you have listened to and deleted all voicemail messages, exit the voicemail system by following the prompts or hanging up the call.
4. Reset the phone: Disconnect the power adapter from the back of your Panasonic phone base unit. Wait for about 30 seconds and then plug the power adapter back in. This will perform a reset on the phone and clear any residual indicators.
5. Check the voicemail indicator: After the phone has rebooted, check if the voicemail indicator is still active or if the light is still flashing. If the issue persists, proceed to the next step.
6. Disable visual voicemail feature (if applicable): Some Panasonic home phones offer a visual voicemail feature that may trigger the voicemail indicator and flashing light. To disable this feature, consult the user manual for your specific model and follow the instructions to turn off the visual voicemail function.
7. Contact Panasonic support: If you have followed the above steps and are still unable to remove the voicemail indicator or stop the flashing light, it's recommended to contact Panasonic customer support for further assistance. They can provide specific guidance based on your phone model and help troubleshoot the issue.
Remember to consult the user manual for your Panasonic home phone model as the steps and features may vary slightly.
this video might help

You probably have unheard messages on the voicemail system provided by your telephone company. This system records messages when someone calls while you're already on the phone. Please contact your telephone company for instructions on accessing their voicemail system.

This isn't a user replaceable part. I would replace the set.

You have unheard messages on the voicemail system provided by your telephone company. This system records messages when someone calls while you're already on the phone. Please contact your telephone company for instructions on accessing their voicemail system.

What voicemail do you have?
Vm Pro or embedded?

If voicemail pro, you will need to navigate to the folder where your messages are stored on the pc, delete them, then stop/restart the vmpro services. If you dont know what I am talking about, I would call someone in that is a knowledgeable tech....

This feature is country dependent and may not
appear in some countries.
If you have subscribed to the voicemail service
from your local service provider, icon turns
on when you have a new message in your
mailbox. After you have accessed to all the new
messages, icon will turn off automatically. If
you find that the message waiting indication
cannot be turned off by the network, you can
still turn off the message waiting indication with
your phone by the following step :

In idle mode, if voice mail waiting icon is on,
long press the redial key to turn off the voice mail waiting
icon.
Once you choose to delete the message waiting
indication, all the other handsets registered to
the same base station will turn off the message
waiting indication accordingly.

Press down the "find handset" button until the paging beep stops (about 5 seconds) and this will reset the indicator lights on the handsets.

1) Press the Reset – Press and hold the ON button for about 10 seconds
2) Make sure the game is inserted far enough into the system, and that it is pointing in the right direction. You may occasionally need to clean the contacts.
3) Also, make sure you are using the supplied power cord/adapter, not batteries. Batteries cause more problems than they’re worth.
-Tha Mp3 Doctor

What worked for me was to call my phone from another phone and leave myself a voicemail. I then went in and retrieved and deleted that voicemail. Once I hung up from my voicemail service my handsets reset about 10 seconds later.

I hope this helps!