Open your rejected bug report and then click the Dispute Rejection button. You will have a chance to edit your bug report to add more information or attachments, and you will also be able to write a message with your dispute that will be sent to the team for further review. When doing so, it is important to remain calm and professional.  Based on new input, your bug might be finalized to either accept or reject by the customer or the testing team.

Check on this article for more details: https://www.uTest.com/academy/tracks/17/courses/bug-rejections