Refund owed for service - Chubb not responding

Chubb came to my residence on May 18 for a service call. I paid via EFT that same day, using the number on the technician's worksheet as a reference. An invoice arrived May 25 with reference ROU*** - I emailed them that day to ask that they note my 18 May payment against that invoice.<br> <br> But then, on July 1, they direct debited my account for the service call. I called them on July 2 - the accounts department promised to investigate, and get back to me - they never did so. I emailed them again on July 4 to request a refund, and have had no response to either email (or call) to date.