Clearly, charm can be cultivated. If you’re completely clueless about how to appeal to others socially, there are probably a lot of quick improvements to be made. There’s simple stuff like using affirming language—saying “I hear you,” or equivalent, at the right moments—that goes a long way. (I learned this from a book, by the way.) If you can’t hold eye contact, learning how to do that is probably good.
However, charm that seems too cultivated becomes unappealing. There is a certain threshold at which the effort to be charming starts to seem robotic and artificial.