You can change your Podbean username/subdomain after you've signed up one. To do so, go to the "Account"->"My Account" page in your Podbean account. Then click "Edit" to enter your new username/subdomain and click "Save Changes" button. It will take about 2 hours to make the new username effective. 

However, it is important to note that this changes the url of your podcast, which can affect your podcast in various ways.Some of the effects of changing the username include:

1. If you use the embed feature to embed the podcast player on other websites, the old embed link will no longer be correct due to the url change. Therefore, those embed links may no longer function.

2. Images embedded elsewhere may not link properly due to the url change.

3. If your podcast is in iTunes, to update your podcast feed in iTunes, please refer to Change your RSS feed URL in Podcasts Connect.

4. There are other possible effects of this change since your url will now be different. Please be aware of these potential concerns before changing your username. If you have questions, you can contact Podbean support.