Can I mention company names in a fiction book?

Yes. You certainly can use these names in your book. Of course, you cannot represent or suggest that your book is affiliated with or endorsed by any of these organizations. But otherwise you should not have a problem Nonetheless, before publishing any book, it is a very good idea to ask an IP lawyer to review it for purposes of identifying potential legal problems. Assuming you have a publisher, your publisher will probably assist you (as a matter of self-interest) in conducting such a legal review--many publishers have lawyers in-house to handle this. If you are going to "self-publish" or if your publisher does not offer to provide a legal review, then you should retain IP counsel to review the book and help you identify and respond to any legal issues or problems that could result in an expensive law suit.