Is there a way to merge two customer accounts?

This is a great question, unfortunately Recurly does not have any functionality built at this time to allow for two accounts to be merged together. If you have two accounts for the same customer, we would recommend choosing one of the accounts to be the primary account to continue billing through, then move to close the other account to prevent any accidental double billing situations. From within the UI, you'll want to visit the customer's account page, then click on Account Actions in the top right-hand corner. From there, simply click on Close Account and this will cancel any active subscriptions, delete any currently stored billing information, and prevent any new billings from occurring on the account unless reopened in the future.