I've had my bag snatched from me before I've even got anywhere near till point (cash register). They told me to leave because I'm barred. They won't let me in to get my bag, and they still have it. How can I get my property back?
Go to the police
Taking someone’s property with the intention of permanently depriving them of it is stealing.
Ask a nice police officer to accompany you to the store to help you sort it out.