Vox charges for services they did not provide

Vox supposedly upgraded my connection to a 50/50 line (on 1 July 2021), which I never had the benefit of. They then billed me for a service that was not provided. On contacting Vox, I spoke to Amy, who promised to get back to me. 2 days later I'm still waiting. Is Vox going bankrupt and now are charging people for services they do not provide or is it pure incompetence on behalf of the people working there? I want a refund for this lack of service. I was quite happy with my previous line speed.