The Rapture (1991) on Netflix

A telephone operator lives an empty, amoral life. She and her boyfriend spend their evenings picking up other couples for group sex. But she begins to notice little things - things that point to something far greater than the life she knows. There are the two men who come to her apartment, preaching God; the conversation she overhears between her co-workers; and even a strange, mystical tattoo on the back of a woman joining one of the sex sessions. Eventually, a crisis of faith that nearly ends in suicide leads to her spiritual awakening instead. But later she learns that even after finding God, it's possible to lose Him again.