Useless Sheet street staff

I fail to understand how the people at Sheet street in Oxford street in East London are unable to do their work, or do they not receive sufficient training before working on the floor. I received a voucher that can be retrieved on my account and the cashier did not know what to do, and instead told gave me incorrect information. Even when one calls in to the store somehow they never answer the phone. Why dont they just close the store if they dont want any business.