imperfect subjunctive, pluscuam subjunctive, or condicional.
Si me (decir) ____ la verdad ayer, les (escuchar) ____.
Use imperfect subjunctive, pluscuam subjunctive, or condicional
Si me hubieran dicho la verdad ayer, les habría eschuchado.
If they had told me the truth yesterday, I would have listened to them.
That is conditional perfect; not conditional.
The action is in the past, not referring to the present or future.
Contrast it with the present:
Si me dijera la verdad, les escucharía.
If they told me the truth, I would listen to them.
In contrast, an unreal or contrary-to-fact condition is one which will not come about or is viewed as being completely hypothetical. In this case, the if clause in normally in a past subjunctive tense, and the main verb is in a conditional tense.
Present or future time situations. The imperfect subjunctive is used in the if clause, and the conditional in the main clause:
Si yo fuera rico compraría un coche.
If I were rich [I am not rich] I would buy a car.
¿Qué harías si fueras presidente?
What would you do if you were president? [you aren't]
Si Juana estuviera aquí, ¿le dirías la verdad?
If Juana were here [she isn't here], would you tell her the truth?
Past time situations. Past perfect subjunctive in the if clause, conditional perfect in the main clause:
Si la hubiera visto, habría dicho algo.
If I had seen her [I didn't see her]
I would have said something.
Si hubieras venido, te habrías divertido mucho.
If you had come [you didn't come] you would have had a great time.
¿Habrías ido a la fiesta si yo la hubiera planeado?
Would you have gone to the party if I had planned it? [I didn't plan it]