If we presume that it’s a technical limitation on their end, albeit sad, they could communicate this better.
Support via messaging is very much part of the user experience of any and all brands. And they missed this opportunity to prove themselves and make up for their technical ineptitude.
It could have went more like this:
“We’re sorry Anton. Due to the technical limitations in place, we do not currently have the ability to remedy this issue. We understand this username is of value to you, and in fact used to belong directly to you. However might we suggest an alternative username that could suite your needs. We value your experience with us and hope we can resolve this for you. Again, sincere apologies — have a wonderful evening.
Actual person + direct email