When your review is published, it shows your first name by default. If your last name is appearing on it, it is because of how you have saved your First and Last name in the Profile page.
We cannot amend a review once it is published, but we can raise a request to remove it altogether. After which you can Change the way your name is saved in the Profile Page and post another review.
If you want us to look into this request please send us an email to email@example.com and we will help you out.