When the gang gets the land-line, they act as if they are using a land-line for the first time in many many years and Jess referred to her idea of getting a land-line as crazy/insane; but in episode 10 of season 2, "Bathtub", they already had a land-line and acted normally around it.
During the conference call, then immediately after when Schmidt calls Winston, Schmidt's and Winston's phones do not behave like they would on a real call. The screen on Schmidt's phone (a Samsung Galaxy S5) changes orientation, both screens stay on the whole time, and both change what they're displaying throughout, particularly evident by the changing colors, especially with Winston's phone. These phones would actually turn the displays off when held up to the ear, and the call screen remains the same and doesn't change orientation.