I want to connect my phone and now an answering machine to the same jack. Is there such a thing as a line splitter

Sure, you can buy them in any Radio Shack or Walmart or even some grocery and drug stores.

Can get them from any dollar store

Many answering machines come with an "output" jack on the rear - so you plug the answering machine into the wall jack and your phone into the answering machine. If your answering machine doesn't have that feature get the splitter at Radio Shack.