Automatic voice mail message + no option for caller to leave a message

I'm hearing impaired and struggle with messages left on voice mail, to the extent that I disabled this feature.
What I'd like would be the ability to have a pre-recorded message which asks the caller to send me a text or a WhatsApp message but doesn't let them leave a voice message.
(When I asked Lebara some time ago, they confirmed that this functionality isn't available.)

Hi suepc1, welcome to the community and thanks for your message! You can customise your voicemail greeting by dialling 121 from your Lebara mobile then follow the instructions. Please let us know how you get on and if you need any further help.

I have been told by Lebara that it's not possible to have a custom message and disable the function which allows people to leave me voicemails. The only way to stop people leaving me voicemails is to turn voicemail off completely - is that now not the case?