A 26-year-old woman presents to the GP with a 2-year history of cyclical right iliac fossa pain. She underwent a diagnostic laparoscopy 6 months ago which confirmed Stage I endometriosis with superficial peritoneal deposits. The deposits were ablated at the time. She is now experiencing recurrence of her symptoms. She is not planning pregnancy and has tried the COC continuously. Which is the single most appropriate next step in management?