What does it mean when he doesn't call as he promised he would?

Only he can really answer this question. However, there is various reasons, he may just not want to talk to you, he may have forgot, he may be busy, he may not be able to use the phone there could be one of many reasons. You may want to ask him or relax let him come to you - if he wants to call he will if he doesn't don't let it bother you - enjoy life, move on and have fun!!