Cool. I'll try that.
The government has the do not call list (www.donotcall.gov) which for the most part works great. I highly recommend everyone register asap (unless you are lonely and enjoy talking to telemarketers).
Being customers, the government dnc list does not apply here. D* can give you a call becuase you are a client of theirs.
As already suggested, I too simply took a moment to tell them to take me off the call list (rather than just hang up or worse...). I said I'd wait while he made the change. No calls since.