I have deleted some text messages by mistake can I retrieve them

The only way to retrieve them is if you have a backup of the phone while the messages were on it, and then you can restore to that backup. Remember, when you restore the phone, it will be brought back to the date/time of the backup. Anything done since that date/time will be lost.

You will not "have a backup on [my] phone." You may have a backup of your iPhone ... if you created one. It would either be in iTunes or iCloud.