Support → Customer → Edit
You can change the Customer name, not the email. Email can be changed from Dashboard > Users > All Users > Search for user > Edit the Email > Save Changes.
You can change the value of the Customer field.
Customer records can be deleted using the Delete option. This will delete customer info, customer field info, and Tickets belonging to the customer. If you delete the customer from Dashboard > Users then it will not delete the entire data of the customer, ticket, and customer info will be kept in SupportCandy.
Logs will keep the records of changes made in the customer fields.