According to the New York Times, AT&T saves deleted text messages for up to 72 hours, and in most cases, it is impossible for a consumer to retrieve text messages once they have been deleted. However, AT&T can provide a record of the numbers that sent texts to a particular phone and the numbers that were texted by that phone.
If a consumer has an iPhone with their AT&T service, they may be able to reclaim deleted text messages using iTunes. To recover deleted texts from an iPhone, one simply needs to connect their phone to iTunes, prevent the phone from syncing automatically, and then, click "restore from backup."
As long as the person selects a backup in which the text was saved, the deleted text should be recovered. This retrieval method works with all iPhones regardless of which carrier the person uses.