My advice: Be honest with the toy store lady. Don't burn any bridges. Tell her what happened and how you are supposed to start on Mon. Take the cell phone job. Tell the toy store that you are going to see if it works out. But if it doesn't, is the door still open for you to come back at talk about possible employment? I mean, how pressed is she to find someone. Can she wait a couple of weeks? If so, she will appreciate your honesty and realize that's a virtue not found easily. Maybe she'll counter-offer.