Hi gopekto2
I'm sorry but VM don't provide a customer facing email contact.
They can contact VM via WhatsApp on 0780 3089 684
Or via Social Media by either messaging
Facebook: https://www.facebook.com/virginmedia or Twitter: https://twitter.com/virginmedia
The inlaws could register and post their issues on this forum and forum staff may be able to help.
They could also ask for your name to be added to the account so you can talk on their behalf, however yuo wouldn't be able to make any contract changes or cancel the account.
Next time the inlaws have any form of dialogue they should ask the agent to register their accessibility needs. There's a link on the following page explaining about the accessibility needs which includes priority support along with links to alternative contact options.
https://www.virginmedia.com/help/accessibility
There's also an online chat messenger pop up on the right hand side of the following page
https://www.virginmedia.com/support/help/contact-us