If you need to update all of your contacts, or a big list, all you need to do is import these contacts again, this time with the correct information of course. This option only works if you have imported the contacts with e-mail address.
When you export you contacts from the survey, each contact (with or without email address) has an contactID. When importing this file again, after updating the information, the contacts will be updated, based on their contactID. This allows you to update contacts without an email address.
In order to start from the correct contact data, you can export your contact list first.