For reservation notifications:
Go to Settings > Services > Stay > Options
Tick off the options which make a new order generate an email or a notification:
You can also adjust the Responsible Employee or department by scrolling down to the Responsibility section
This is the department or employee that will be notified by new reservations:
For merchant notifications:
Head to Settings > Marketplace > My subscriptions > Merchant settings
However, this contact will only be changeable by the Customer Care team.
Make sure the one in use is incorrect and contact the team.