1. Will you call me? (Asking for possibility whether he would call her or not). 2. Will call you? (Offering something in this case he offered to call her).

The second example is not really a question and it's definitely not a sentence because it does not have a Subject. The Subject of the sentence is understood, that speaker believes that the listener will know that the Subject is missing. The missing subject is usually the pronoun "I". So, the sentence is really "[I will call you." (NOT a question)]