Please reach out to podcasters-support@spotify.com with your request and the Spotify team will help you out. 

To get help faster, please include the name of your podcast, the link to your old and new RSS feeds and the email address of your Spotify account.

You can contact them directly though this link:
https://support.spotifyforpodcasters.com/hc/en-us/requests/new?ticket_form_id=360000956072