If you have multiple bookings for the same guest and each booking contains the same guest information, you will find that changing the details on one booking will automatically update all other bookings for that guest as well.
If this is not what you want then follow the steps below.
1. Multiple bookings for the same guest creates a link meaning all the bookings are linked by the guest name.
2. If you wish to only update the contact details for one booking then navigate to your chosen booking and click "Add new customer".
3. Now you can create a new customer record and Save.
This will assign your new customer to your booking and leave the other bookings as they are.