What is the name of a movie in which girl has to babysit kids while their parents are gone and later on she gets weird phone calls it turns out that there killer with her inside house?

You're likely thinking of the 1995 horror film "The Babysitter."

Here's why:

* The plot: A teenage girl is babysitting two young children when she starts receiving strange phone calls. It turns out there's a killer hiding in the house, making the babysitter and the children his targets.

* The killer: While the movie doesn't focus on the killer's identity or motivation, the element of a hidden, menacing figure is a key part of the suspense.

There are other horror movies with similar themes, but "The Babysitter" is the most likely candidate based on your description.