You will need
Open in your phone's "Menu".
Select the tab "Messages".
Press key – arrow down to find the tab "Deleted messages".
Open the folder and view the messages. Which have been removed. You can restore them using the tab "Restore" or "move to read".
Try not to delete those texts which have a password to access a particular website, Bank code, etc. Record and store them separately. If you lose important information to read deleted messages from the phone will be impossible.
You can order the service to scan text from a phone on a separate printed sheet. And even in the absence of the tab "Deleted messages" you can ask for help to the operator.