USELESS - overcharged for 4 months and nobody cares to respond!

Since the re-opening of Virgin Active gyms following lockdown, my account is no longer linked to Momentum Multiply and as a result I am being billed at the full membership price and not at the reduced rate. I have over the past four months sent dozens of emails, online form submissions as well as engaged with my local club [Waterfall] and called the call centre. All of which have not resulted in any resolution. As it stands I am now owed a refund for the past four months of incorrect billing as well as any future months. Please can someone at Virgin Active engage with me on a resolution as none of the other contact methods seems to get any response.