Yeshivaguy-
Although we all do things to hurt other people, if you forgot, that means you probably don’t care anymore, in which case it’s very easy to be mochel, because if you don’t care, then you’re Mochel, and asking for mechila is almost just technical, although there is an inyan for you to ask, another reason that tfila zakah isn’t the best option. If it’s something you remember, it’s probably something significant that the other person maybe hasn’t gotten over, so you should call and really apologize.