Over-debited me, but no response to my query in 16 days, despite follow-ups from me

I emailed a query on 21 Feb about why I had been debited about double the amount I am usually debited by Virgin Active. Got the standard automated email response. I followed up 48 hours later. Then another 30 hours later. Now, 16 days later, still no response!!! What an utterly useless bunch.