How can I retrieve deleted messages?

IF you have not activated iCloud Messages and IF they are included in a backup you have made you can restore from that backup. You will lose anything added since the date/time of that backup.

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Gators0 wrote:

How can I retrieve deleted messages from my iPhone?

if you weren't using this click here Keep all your messages in iCloud - Apple Support

and have been doing this click here How to back up your iPhone, iPad, and iPod touch - Apple Support

then you recover here Restore your iPhone, iPad, or iPod touch from a backup - Apple Support