"Hamnida" (합니다) is more formal than "haeyo" (해요). I would ask a friend or read a guide on formality/speech levels in speaking in Korean. Both belong to the root verb "하다" (to do). "Isseoyo" (있어요) has a different meaning and means "there is" (root = 있다). There are a lot of different conjugations because of the different politeness levels. Good luck!