R u absolutely positive that poland is not issuing work permits for admin and cashier jobs?
The prospective employer has to apply for one and there has to be a very good reason for the state to grant one - it's usually for very specialised jobs. Remember, there are millions of unemployed people in the EU who already have an absolute right to live and work in Poland.
Plus, in two decades of living in Poland, I have never come across a sales cashier who does not speak Polish - in fact, most do not speak English.