These two phrases never cease to confuse me. I always say: 

* *Je les ai envoyeur mon message*
* *Je les ai dit de ne pas me perturber*
* *Je les avais fait comprendre la phrase ...*

So on so forth. I can not distinguish when it is appropriate to use "*Je leur ai...*". 

For me, "*Je les ai..*" sounds a lot similar in meaning to "*I ... them*" 

Is there some sort of mnemonical solution to understand their use-cases?