It's increasingly difficult to change account's email and phone number, some services require selfie or scan of identity document. The fingerprint consisting of email and phone number is slowly becoming digital DNA.
I didn’t run into the issue you mentioned, but I ran into the issue of Sony (for the PSN) telling me they wouldn’t delete a duplicate PSN account I had (conflicting with their support docs), after I waited 40 minutes to speak to someone. When I tried to bring up the support docs they ended the conversation.
I had a similar issue with Rockstar, where I ended up in captcha hell, having to solve 30 puzzles in a row for each login attempt or and again to get into areas of the site to change things. The site would not function. I got fed up to the point of wanting to delete my account. I don’t use it anyway. I did whatever the site said to do, and it said it could take up to 30 day(?). That was probably 3 months ago and I haven’t heard anything.
These two things make me uncomfortable deleting one of my Gmail accounts, so it’s still hanging out there.
I am currently paying for a US phone number I don't meaningfully use, because it's not clear that all of my important account-holding organizations reliably support a two-factor/login confirmation strategy that isn't "US phone number".