I don't have an answer for you, just some things to consider.
It sounds like you are not currently a Dish customer, but a SBC customer and just sending the Dish part of your bill to Dish; both before and after cancelling your bundle.
I wouldn't be suprised if you weren't leasing your equipment through SBC or their affiliate.
I've seen a few posts where people were told to ask for the "retention department" and tell them you are ready to scrap Dish because.....
And likewise, I've seen where some have gotten favorable results by emailing the CEO at Dish.
Maybe someone will respond with the email address for the CEO.
I would tell you to play Russian Roulette with the CSR, but you have already called too many times and its not working. Maybe ask for a Supervisor as soon as someone comes on the phone, but I think now just skip to the retention department.
If you were a customer through SBC, then you should be a new customer to Dish. Before calling anyone, check out the deals they have for new and existing customers on their web site or the web sites of retailers, decide what you want (maybe with a commitment or not) and then DEMAND they make your life easier, or you will be a new customer, but at DirecTV.
I like the ViP622. Some wish it had a 2nd OTA (ATSC) tuner, I wish it had a NTSC and/or cable tuner. I'm thinking about a 2nd and maybe a 3rd ViP 622, but am waiting for the TIVO suit to get resolve.
EDIT: Post number 6 in the following thread has the email address "CEO@echostar.com":
http://www.satelliteguys.us/showthread.php?t=83443