I chose a username, tyrell0570, however in the app it shows a bunch of random usernames and i can't stop, but being annoyed by it. I connected to facebook and it still the same. I got spotify premium on it because it was just the username i had chosen. Then it changed.
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Welcome to Spotify Community and thanks for reaching out here!
Actually, when you choose a display name, even if you connect your Spotify account to your Facebook, the name you've chosen is the one that will appear on your profile, playlists or the app.
If you've chosen a display name, but it seems to not work well and you're seeing a bunch of letters and numbers instead of your display name, I recommend that you go-ahead this Ongoing Issue thread and provide us the required information.
On the other hand, you can always start over with a new account following the steps in this Spotify Answer.
More information about usernames or ways to "change" it here:
If you have any other further questions or need more help, let me know! I'd love to help!