Nowadays telephone polling is conducted with both land-lines and cellphones, since land-lines are being phased out from usage.
As for USA 2016, their federal polls were not that far off. Most were predicting a Hillary lead of 4%, and she ended up with a 2% popular vote lead. That's within the margin of error. It was like a statistical miracle that Trump won the states he needed to win, while losing the popular vote by 3 million.