Ramadan:If we are not allowed to change Allah(swt) creations then why?

Yes, we`re not allowed to change any of our body parts except if it causes an extreme pain or death, infected by disease or severely damaged. Circision is a necessity because it prevents any plague that can infect our private part and besides that, it`s about cleanliness because we don`t want any hadas(urine etc)on our body parts while we`re praying. From what I know that circision in Islam does not remove any nerve but just the outer skin.