Yes you can access internet even if you cancel the voice service on the modem so you just need o make sure whether your modem is activated by Xfinity properly to get internet service.

I don’t quite understand.. I am already connected to the internet. I want to know if when the moment the voice is turned off, will it also temporarily turn off my  internet, where I have to call someone to adjust my modem settings?

Since the modem Tm822 is not compatible with Arris, I suggest you to contact your internet service provider for further assistance.

Why is an Arris TM822 not compatible with Arris?

Because its supplied to ISPs and not purchased directly from Arris. 

The ISP supplied devices are supported through the ISP’s support and not arris. 

but your service should still work fine if you cancel voice. 

I bought the Arris directly from Amazon. It’s not the question of whether it will still work, it’s the question of whether when at some point during the day when my Voice is shut down, will my modem shut down at the same moment and need some kind of “adjustment”  to make it work again that I don’t know how to perform.

You did. but there are a ton of resellers on there. Might have been a 3rd party. 

Plus it might be time to upgrade. The TM822 is a older 8x4 modem. its the most base model docsis 3.0 modem you can get. Xfinity has been increasing the requirements on their modems for decent speeds. 

You might see a nice speed bump by upgrading modems. You might even checkout their approved modems for their increased upload speeds.