Is Christianity just change of life or dharma itself?

Many believers entangle with this issue whether they really changed their dharma or they just changed their life (transformation). Usually, they are taught, being a Christian isn't changing religion. They are taught Christianity isn't a religion but relationship with God. I have brought a different analysis and insight on this topic and how we can deal with this issue properly. P.S. I apologize for background distraction. The basic definition about dharma and its explanation has been taken from "The Major Religions of the World" by Rev. Dr. Balkrishna Sharma.