Ask HN: Someone has taken control of my domain from 123reg

Last month I noticed that DNS wasn't resolving for my domain, which I manage through 123reg. At the start of this month, someone else's website was hosted on my domain and the nameservers are now cloudflare. Worryingly, the single purpose of the site in question is offering to sell the domain. I opened a ticket on the 9th of May with 123reg detailing the issue, had some very slow back and forth with the support team - who were telling me how to reset the nameservers and not really investigating the issue. It's now the 25th of may and my last communication from them was the 23rd of may: Hi, Hope this message finds you well. This matter is being checked. We will come back with an update as soon as possible. Regards, Has anyone experienced something similar? Any idea how I can escalate this beyond 123reg?