I got her 4 days ago, and she doesn't come to me when I call her, I try to play with her, she would not play with me

You got her 4 days ago. Give her a chance to get acclimated with her new home. It needs your love and attention right now, she will play and come to you after she learns to trust you and her new surroundings.

That is also a sign of worms... get her checked at a vet.

As Cliff said give her some time, it's a huge adjustment for them to make. Just think, they go from living with their brothers, sisters and mother all their young lives and then all of a sudden they are taken away by a complete stranger.

Dogs have different temperaments, some are very outgoing, others can be very shy, perhaps you have a shy or timid dog... Or maybe even a really laid back puppy. What was the pup like as it was growing up? Did you visit the puppy at the breeders to see how it's temperament was?

A vet check is always a good idea with any new puppy, especially from a not so reputable one who sells underage puppies.

7 weeks is still pretty young to leave the pack. It's illegal in Canada and some states in the US to re-home a puppy under 8 weeks of age. She is going to need time to get used to her new family with out her litter-mates.

Dogs don't understand the English language, you have to teach her those commands such as come, here and sit. It all takes time and practice. Bring her to the vet for a meet and greet, have her vaccinated for parvo and treated for worms and fleas (oh by the way, a new puppy being shy is NOT a symptom of worms... ), get her in a puppy socialization class, and take her to obedience classes. Is this your puppy or a family pet?