12Go support do not respond to problems with bookings

I booked a trip with this travel booking site. They overcharged me by adding Covid insurance which was not chosen. I have sent several emails to their support team with screenshots, submitted 3 support requests through their platform and nobody replies or sorts this out, despite them claiming they have 24/7 support. They cannot be phoned so I cannot speak to an agent to get a refund of the overcharge. Very unsatisfactory.