Sometimes they put ads to look for staffs without mentioning the extra part but let the girl do trial for few days so they actually don't know about extra. And actually it's their choice to offer or not, like your choice to take offers or not. Sometimes they think you're detective so they refuse to do, etc. it's not so serious but 121 can offer extra by another girl when the first one finishes part one. Sometimes shop does that. Anyway, 121 manager tried to be nice and offered compensation for you already. Take it easy and give her another chance. That's my 2 cents. Cheers.