Well, the D3 Voice Equipment for $7 is the modem lease fee. That is a monthly charge, depending on your area, you can purchase your own eMTA modem and return the Comcast modem and avoid that charge.
The HSI SIK charge is a one time charge for the kit that you were given, including the cables to install everything. That charge also varies depending on your area, I am not sure what in your area it includes, but if you contact the billing department at 1-800-Comcast, they can give you more detailed information.
Comcast Nick Supervisor Executive Customer Relations
I just reviewed my bill and see this same charge. I started with comcast in March. I used their modem for 2 weeks. Here is my first bill.
High Speed Internet $29.99/mo. Promotional Rate 6 Months Modem Rental $8.00/mo.
Then I switched my own modem. They do not charge the $8 for the modem, but they charge a $8 D3 Voice Equipment fee. I have no idea what D3 Voice Equipment is, but it should not be the modem because the bill explicitly states my Mdm cost is $0.00. I should have check my bill more closely. This autopay option is so convenient. I did not realized they charged this D3 Voice Equipment fee since April.
XFINITY Internet Docsis 3 Owned Mdm 05/20 - 06/19 0.00 D3 Voice Equipment 05/20 - 06/19 8.00 High Speed Internet 05/20 - 06/19 66.95 Performance w/o $29.99x6 -36.96 Total XFINITY Internet $37.99
Docsis 3 Owned Mdm 06/20 - 07/19 0.00 D3 Voice Equipment 06/20 - 07/19 8.00 High Speed Internet 06/20 - 07/19 66.95 Performance w/o $29.99x6 -36.96 Total XFINITY Internet $37.99
Comcast told us this evening that the SIK charge is for "activation". So I guess 9 different people will get 9 different answers to "what is this?". But SIK is an abbreviation for "Self Install Kit which implies some concrete hardware, etc.
Comcast is a BS company ... cover your wallet and your "a $$".