If you have a c/mute button hold it down for a few seconds and see if this helps remove the icon. I am only saying this as a while ago we had a Customer with a Panasonic Dect Phone, Who had the same issue, Then by accident he tried that and its removed the logo
I'm guessing that you have tried deleting any voicemails as well
Thanks for the reply. I was thinking about that. But there was no option for me to read it. So I've sent a text from my mobile tp my landline and it came with a call. With this experiment, I've concluded that it was not a text message or not one that would've been sent as a standard.
I've then sent another one and did not picked up the call. It went to VoiceMail (VM) and the icon for VM was different than this one.
Thank you so much for this idea. I would've not thought about it. And now I know how text messages work on the landline.
I've done a full reset of the handset and deleted all the VMs, which made it disappeared.