Tried this, how can you do volume down after power, when it is already down

It's possible that they were backed up with you last backup assuming you had thing setup to backup. Check Settings > backup and see when the last backup took place. If it was before you deleted those text messages then you'll be able to recover them.

The only thing is you'll have to restore you phone to factory default (hold volume down, then connect the charger - then press volume up, volume down, power, volume down in that order), set everything back up from the same email and and then restore from that backup. You should save any data that you want between when the backup was done and now.

Hello! I accidentally deleted some text messages that I NEED to get back. Is there any way to do this? TIA!