GPS requires constant updating from a ground station, so it would depend on keeping that timing correction signal going.  2-3 days after not getting a correction and it will start getting off enough to be a problem.  Unless all the ground stations (and there are some portable ones from what I understand) were destroyed/inoperable it would be maintained as long as fuel and personnel were available.  Commercial satellite internet would be down at the same time as landline since the uplink is connected just like any other node, and the satellites would start wandering in orbit without course correction.  

I think sat phones would be in the same boat without an uplink center as far as calls.  I don't think they can route a call between two handsets even on the same satellite without control from an uplink, but I'm not sure.