ARRIS SB8200 Firmware/Software Update?

I own my personal Modem (ARRIS SB8200). I pay for very fast WiFi, but recently the connectivity and speed has been horrible. I have been trying to contact Xfinity to get them to come take a look at everything, but it feels very difficult these days to get a real person. When the AI runs diagnostics, it just keeps telling me there are no outages and my internet is fast and efficient... it's not. Could this be because my Modem (and possibly Router) aren't up-to-date on the most currently firmware/software? I know I can't do this manually and would need Xfinity as my ISP to push this update through. How would someone recommend I get them to do this for me? Nothing seems to work anymore and I just want to internet quality that I am paying for. Thanks all!