Change my phone number

I recently got a pc because I have been saving and I was using a laptop, I got a razer Huntsman TE for Christmas about 2-3 years ago and I set it up with my laptop and I downloaded the razer apps. In the past couple of years, I have changed my phone number or have gotten a new phone. I have not been able to change my number on my account because I don't have access to the phone number anymore. Dose anyone know a solution or can i get some help changing it.