A useful roundup article on the Neil Patel blog explains How to Change Your Username on Social Media. This is something that was once impossible, or at least very hard, but is now quite a bit simpler on many services. It can be useful if you or your business started off with a name you’ve rather regretted, or if something’s come along that’s made your user name somewhat less desirable. Some businesses have acquired different user names on different services, and might like to rationalise things.
Note that with some services, changing your name makes the old one immediately available to others, so you’ll want to grab that back too. The article explains how you’ll need to update many links as well as tell your followers.