CM500 Modem - ISP won't update firmware

[Grateful-one]

I have Optimum as my ISP and I purchased the CM500 modem that is currently running firmware version V1.01.04.   The latest version that for this modem is the V1.01.12.  I've asked my ISP to update the firmware and they claim they don't do this.  I called NetGear and they claim the ISP does this.  So I'm stuck in the middle with a very old version of firmware.  What can I do.  NetGear said I can purchase a support contract for 3 months for around $50 but the modem itself is worth around $80.  All I want to do is to update the firmware.  Any and all recommendations would be great.

[FURRYe38]

ISP have to update FW. NG or any other cable modem mfr do not offer user FW updates for cable modems. This is ISP requirement. Some ISP won't update user owned modems. So if your ISP won't then you'll be stuck here the modem is at. 

Is there a reason why your seeing a FW update? Is there a problem with the modem? Sometimes you don't need a FW update to fix something. If the modem is working then don't fix it! 

[Grateful-one]

I'm seeing non consistent speeds coming out of the modem with hard coded to my computer during the work week.  Seems better off hours or on weekends.  Wondering if the firmware update would help with this issue.  Optimum claims that there is over 500 mbps coming into the modem and this modem should be able to handle 680 mbps.  Since my computer is hard coded should I receive consistent speed thoughout the day unless the ISP has issues with bandwidth.  Why does over 500 mbps coming in get drilled down to under 40 mbps at times during the day?  

[FURRYe38]

Is your PC directly connected to the modem or is there a wifi router in between the modem and the PC? 

What do you mean by hard coded? Static or Reserved IP? 

Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 

Also with everyone working from home over the past couple of months, you may see odd speeds or inconsistent speeds due to ISP services having to take on more service loads.