In the prior episode (#3.6, A Kind Word for the President), Alf and Ralph finally install the phone in the kitchen by making a hole in the roof to run the wire. In this episode, the phone is back at the top of the pole. However, Alf and Ralph do not move the phone back to the top of the pole while repairing the hole until 2 episodes later (#3.9, The Thing).
At the beginning when Eb is typing and has to answer the switchboard, he walks to the switchboard, you can see the shadow of the boom mic above his head.