An error by a US-based payment processor caused a number of North Rock Communications customers to be double-billed for their June payments.The Internet provider said yesterday it had now credited all of the affected customers’ accounts and that three percent of North Rock’s customers were affected.“We have been working closely with Butterfield Bank to determine the root cause of this error,” North Rock said in an e-mail to customers on Monday.“There was a delay in the bank’s payment gateway which caused the double billing. The charges are being reversed and we hope to issue a refund within five business days. We apologise for any inconvenience this may have caused.”A Butterfield Bank spokesman said: “Due to an error by an intermediary payment processor utilised by North Rock Communications, some customers who settle their monthly North Rock bills by preauthorised payment using a debit or credit card have been billed twice for their June charges.“The vendor is in the process of reversing the erroneous charges and credits will be applied to the affected accounts shortly. Butterfield is working closely with North Rock and the vendor to resolve the matter quickly.”