Not sure what to tell you, I have AT&T, they also rent out modems. When I was trying to connect, the service guy had the nerve to tell me that he has no clue how to have my router + modem connected since it wasnt AT&T model. I laughed at him for a good minute, told him -" Are you honestly trying to tell me that this is how far your skill level goes?", then I said "Ok, I will make it easier on you, lets imagine that my modem is ATT modem, and walk me through the setup same as if I had your modem." Obviously that is where I got him, since they are all largely the same when it comes to software. For you, I would do the same. Considering that server connection has nothing to do with hardware (unless modem gone bad), they really have no right to refuse your service call. After all you are paying for Internet connection, and that is what you are having trouble with.
Is there a way for you to get a satellite ISP?
PS: Stand your ground dont let them bull-crap you