✦ Por favor, dígame la verdad. (Please tell me the truth.)
Now, study this sentence. It is the same verb; however, you are using it in the 'usted' form, i.e., it is a formal command, rather, it is a polite request. Hence, you use the word 'dígame', where 'me' is the direct object pronoun, and 'díga' is the actual imperative form for 'usted'.