How to retrieve the message deleted by the old man?

If you haven't backed it up before, you may not get it back. It is suggested that you can query some records through the schedule.

You can log in to China Mobile official website, click "Telephone Fee Inquiry"-"Bill Inquiry" or "Detailed Bill Inquiry" on the right, select the month to be inquired, and you can inquire the detailed bills of the last six months (including the current month). In view of the different business regulations in different provinces, you can call local 10086 to get more help manually.