VM can be somewhat negligent in sending proper notification that this has been actioned
Somewhat negligent? How about intentionally incompetent? Or maybe just "couldn't give a tish"? When I cancelled a couple of months back I got zero confirmation. Nada. No "thanks for being a customer for over a quarter of a century and paying us over fifteen thousand quid", no "we confirm we've received your cancellation request, and your last day of service will be XXXX", no "here's a detailed final statement, we hope we'll be able to serve you again in future". Even the billing information and next bill alerts were worrying, inaccurate and confusing. In actual fact, my account was closed on time, the last bill was correct (although I'm still waiting for my ten quid credit balance), and I'm now happily VM-free.
The only evidence that I'd cancelled were the significant number of retentions and "research" calls, with five of these on my last day of service. You'd need to be a very special sort of company to behave like this, a Virgin Media sort of company.