While it feels like yourname → infy.uk like infy.uk is just an extension you can change like a file extension, domains doesn’t work like that. infy.uk is “bigger” than the part before it, and there’s no way to “just change the domain from one extension to another”.
The only thing you can do is to migrate your website from one to another.
You don’t have to necessarily delete the domain, and for reference, it not recommended to panic and move away from the domain just yet, sometimes waiting is better.