I've just had business cable installed at home for teleworking purposes. The modem model is SMCD3G. I was dismayed to find there is an unencrypted SSID broadcast by my device. I was even more dismayed to find that I cannot disable it nor can I disable the broadcasting of my installation location and "business name" on the wifi hotspot map. My "business name" is my personal name and thus anyone searching on the map can see my name and address! I believe the network security guys at my employer here in CA will force us to drop
I've been informed by my employer's comcast business contact that I can return the modem and use my own. I've been warned this can take months to process. Until then I need the insecure connection permanently disabled and my hotspot map entry removed. If this is no way to do this I will be forced to cancel the installation through my employer's business contact.
You should be able to return the modem to any local Comcast office. Make sure to get a receipt when you return it. In my experience, the process of returning a rental modem and activating a customer purchased one takes minutes, not months. Be aware that if you are leasing a static IP from Comcast, you MUST rent one of their modems; retail purchased modems are only compatible if you do NOT have static IPs.
You save considerable money for whoever is paying the bill by using your own modem. The rental is something like $15 a month and as stated by the other poster you only need to rent it if you have a static IP