On-Demand

Hey there, I recently accepted an On-Demand position with Target and over the phone HR told me that I would be required to work weekends but am able to pick and choose shifts throughout the week which is very confusing because in the On-Demand Addendum it strictly says that the store is not allowed to regularly schedule you, especially without your permission. Are they allowed to schedule me on the weekends like that? And if not, who else can I contact about it since I’m getting this info straight from HR?