There are a number of reports which prohibit such practices who are not ruqyah in anyway. The incantation of the Prophet included recitation of certain chapters of the Quran such as surah 112, 113 and 114. He also used to make invocations to relieve a sick person from pain. These reports are well known in Al-Bukhari and Muslim. You are not supposed to disobey Allah for the sake of obeying anyone even if your parents. I suggest if they insist to do so, let them burn those papers without paying attention to them or even believing in what they do. You must in all cases explain for them the legal ruling of those acts and warn them against disobedience of Allah by making such superstitious practices which may include magic. You must explain also for them that magic is forbidden and may have evil consequence on you and on them.