Directtv and dish modems

I want to thank those members who clarified local channel reception questions for me in my "possible move" question some time ago. I've since decided that to have what I want, I will need both dish and directtv simultaneously, each service with more than one receiver. But that raises another question. To have more than one receiver from each service, each receiver needs to connected with its twin with a phone line. I can do that but what will happen when two dish receivers are sharing one line with two directtv receivers simultaneously? I understand that there are circumstances where dish or directtv will make calls to a person's home to interact with their equipment for obscure reasons. Is it possible for one provider, Dish for instance, to try to contact the modem(s) in their receiver(s) and end up having directtv's equipment trying to field the call thereby generating confusion? What can be done about this apart from getting a separate line for each service which seems to me excessive. My purpose in getting these satellite services is for them to provide me with entertainment - not for me to entertain them if you take my meaning. Again, thanks for your assistance.

Pete