Transfer customer-owned modem from my account to parents

Hello, I had an Arris S33v2 that I bought from Best Buy and that I used on my home Comcast connection. I have since upgraded to a Coda 56 modem here, and would like to get the Arris transferred to my parent's account. At the very least I would like to make sure that the Arris is completely and totally removed from my account. My dad would like to install/activate at their house on Monday Sept. 23. Please advise, thanks.