You can manually edit any user name and email address in Receptive.
If the user was created through the Receptive API, you can change their details with the instructions here.
Just find the user's account page by heading to the "Customers" link from the dropdown in the top right corner and selecting the correct account from the list.
Select the user from the list on the left hand side.
Then click "Edit":
Then edit the appropriate fields and click "Update":