Red light keeps blinking even with no messages even after all messages are retrieved

you said voicemail, which is a service from the telephone provider. Typically, you dial your own number and follow the prompts. Contact your service provider if this does not work. It is NOT the phone.

If your charge light is flashing and you have no messages on your answering system, you may have voicemail. Voicemail is provided by your telephone company and they would be able to assist you with retrieving those messages.

There are unheard messages on the voicemail system offered 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.

You're apparently subscribed to a voicemail system offered by your telephone company. Contact them for instructions on accessing their voicemail system.

You're probably subscribed to a voicemail system offered by your telephone company, and the phone is telling you there are messages waiting. Please contact your telephone company for instructions on accessing their voicemail system.

#409

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.

Found a user manual online. Solution is holding the "Find Handset" button in for five seconds, until the red light went off; that reset the message waitung light and message.

To reset the indicator(Red light flashing on handset), press and hold the find handset key for 5 seconds or until the light flashing stops(10 sec).

Here are sample paragraphs from the user manual : hope it helps !

The new message LED on the handset flashes when you have new messages in your
answering system. The LED stops flashing when all new messages are played back.

3) To delete all messages, press delete messege in standby mode. Press delete
messege again after the announcement "To delete all messages, press delete
again."
When you try to delete all messages without first listening to your new messages,
you hear several short beeps followed by an announcement "Please playback all
messages." This protects you from accidentally erasing messages you have not yet
reviewed.
Important:
When you press delete messege, you are permanently deleting the message. Once
deleted, the message cannot be replayed or retrieved.