They can now call from home. I'm guessing they'd call people, say they're from the GOP, the folks will believe them because they had to get their number SOMEHOW, and they'd say or do something to try to get the person to either not show up to vote, or to turn against the GOP. It's a simple and dirty strategy.
Either that or they won't make the calls. If they were to try insulting the voters or the R candidates, they run the risk of being exposed as people would call news stations and the GOP to complain.
Or...We rely on them to make the GOTV calls for certain areas and they are not making the calls.