Sounds like we need to adopt non existent grandchildren when we answer the phone so when we say the fake name our real grandkids will say no this is (real grandchild name)(Just make sure your family knows why you're doing this). These scammers wouldn't know you have an non existent grandchild and would say yes. You could then, if you have time, play with them telling them all sorts of things taking up their time. If they mention being in another country start making up a story of traveling when you were younger and how those were such good ol days. If they ask for money your answer was perfect - gas and electric bills are others.
I do appreciate your reminder to us. Thank You!