I think I might be able to shed a little bit better light on this on why the installer canceled the job as I have run in to this situation before.
It sounds as if you have a box inside that has all your cable connections with a single wire that runs outside.
Where under normal circumstances this is fine for SWM, you have a cable modem which uses that single wire that feeds outside.
Now, seeing that that you live in an apartment, the installer may not be allowed to run additional lines and they restrict you existing cable.
If so, you will have to cancel comcasts internet service and go with DSL.
It also may be possible they will allow you to run a line but impossible to get it to the "Q box"
(Some examples would be if it is if you are on a bottom floor on a slab, middle floor, or top floor with no attic access and the box is not on an exterior wall)
If this is the case then again you would have to go DSL the get DirectTv.
If the installer can get to that box though, and is allowed to by the apartment complex there are no issues.
It just may mean you don't get an internet connection depending on how that room is situated.
If not, it may mean running new lines to everything, but again, the tech needs permission from the apartment management.
Two things you need to do before rescheduling would be to figure out of a line can be brought to that box.
If so, get permission from the apartment management to do it.
If not, then figure out if you would rather have DSL and Satellite or just stick with cable.