To dream that someone is calling you a liar denotes that you will be irked by some deceitful person.
To dream that you are lying suggests that you are trying to deceive yourself into believing in something that goes against your natural instincts or long held values. Ask yourself what you are hiding from yourself or from others.
To dream that someone is a liar indicates your growing distrust for that person. You may have lost your faith in that individual. Alternatively, it suggests that you are no longer as confident.