 you owe them for their embracing islam. tell them you are not doing me any favors by embracing islam. in fact it is god who has done you a great favor by guiding you to the faith. if you are people of truth.
يمنون عليك أن أسلموا قل لا تمنوا علي إسلامكم بل الله يمن عليكم أن هداكم للإيمان إن كنتم صادقين