It depends on the reason. Something may have happened that prevented that person from calling you and it may not have been their fault. In that case, it is not grounds for disbelieving everything they say. If they did merely lie about the fact that they were going to call you, then it would be grounds for being doubtful about what they say to you, not for automatically disbelieving it. Automatic belief and automatic disbelief (except in the case of a compulsive liar) are equally foolish; no one lies or tells the truth all the time. Best to remain reasonably skeptical and give those you have reason to trust the benefit of the doubt and to be doubtful of those you distrust.
You neglected to give me your phone number.
Are you sure that's the right number this time? 1 800 SPA NKME didn't work.
He'll no I'm iris would charm the birds off the trees
I suggest you ask WHY the call you were hoping for didn't happen. Depending on the reason, then decide whether to believe or not.
Just believe what you feel ....