Unless you had them backed up somehow, once they are deleted from the phone they are gone.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
To access past messages, they would need to have been backed up via backup app or Verizon Messages before deletion. Did you have them backed up beforehand? There isn't a way to get your messages back after deletion if they were not backed up. (Technically, you CAN get SOME messages via transcript from Verizon, but only within a few days of reporting and only with a court order)