Oh My Goddess! Final Exam

Oh My Goddess! by Kosuke Fujishima. A Romance manga rated Teen, published in English by Dark Horse.

Hapless college student Keiichi Morisato dials a wrong number and reaches the Goddess Help Line, and the beautiful goddess Belldandy appears to grant him a single wish. Half-joking, he wishes for her to stay with him forever, and the wish comes true, bringing heavenly chaos to his everyday life.