Hello aepod,
Thanks for reaching out to the Apple Support Communities! We understand you are looking for some help with changing the swipe actions that are displayed in the Mail app on your iPhone. We are happy to help provide some guidance.
If you are using your iCloud mail account in Mail and wish to change that behavior, try the following steps.
Go in to Settings > [your name] > iCloud and swipe to the very bottom of that page and choose the option for Mail. When you are in Mail, select Advanced, and look for the section titled "Move Discarded Messages Into", and change that to "Deleted Mailbox".
Let us know if that helps or if you are using a different email account such as Gmail with the Mail app.
We hope this helps!