If there is not a custom message for the 1st, (7th and 21 for Version 7 or higher) day billing failure message the following message
is the default message that is sent out to those customers:
We attempted to process your credit card that is on file with yoursite.com and the charges were not accepted.
This payment failure may be a result of your credit card number or expiration date changing.
If you wish to renew your subscription to yoursite.com please visit
These message can be customized under 'Edit Site Descriptions' --> 'First Billing Failure Message', '7 Day Billing Failure Message' and '21 Day Billing Failure Message'