If you make changes on SoundCloud, they will automatically update your RSS feed. From there, it is up to Apple Podcasts to refresh its cache and recognize these changes. It can typically take up to 24 hours for Apple to update your podcast.  

If you are unable to see the changes to your podcast on Apple Podcasts after 24 hours, please reach out to them directly. From SoundCloud’s end, we can only recognize that the changes have been made in your RSS feed properly. As a hosting provider, we do not have any influence over when Apple refreshes its cache and updates your podcast.