Appaling State of Call Centre

For the past two weeks i have been trying to contact Virgin Active to have my membership cancelled. However when contacting the call centre i cant seem to get through. For some reason whenever i call, be it morning or afternoon they are experiencing high call volumes. Its been four tries now of being on hold for over 30 minutes on the phone but i still cant get through. Tell how do i cancel my membership? should i just block the debit order?