Mango voucher requests

Mango has failed to reply or respond to my request for 3 days regarding a flight voucher after they changed the flight time. Calling the helpdesks at different airports has also not helped, and I am not willing to wait on the line for 30min once calling the general enquiries line. Contacting them on Facebook seemed hopeful as they were replying to comments on their wall, however once "popping them an inbox" I am still waiting for a genuine response that is not automated. My flight is on 05/10/2020 and I need to know that they are willing to offer a voucher before my flight.