Poor customer service.Rudeness and no regard for customers

I entered OK foods cambridge just before 7pm on the 4th of December.i approached cashier at kiosk needing to purchase a 1FOR you voucher.i was then told in a very rude manner that it was offline.i ignored the rudeness and continued on my way to purchase other items I needed from OK foods before work...I approached the kiosk again and as I was paying for my items.bare in mind that I am a regular customer at OK foods cambridge and have been a customer at this store for years...I asked in a very respectful manner just out of curiosity as to maybe would the cashier have any information on what caused the 1FOR U purchase to be offline and she abruptly and rudley said to me that it's offline and no she doesn't know would I like to call the manager or what because us as customers like to call the managers...I rep**** by saying what was the need for her to be so rude and involve the manager when all I was doing was asking a question.one of the worst experiences I've ever had at this store.she was loud and did this infront of other customers showing no respect for me as a customer and I said to this cashier that she needs to learn how to treat customers or OK foods cambridge needs to educate this cashier on customer service because she was completely out of line and this is not the first time ive experienced such poor customer service at OK foods cambridge in east london...nothing will be done to resolve this matter or deal with this individual that I can assure you as OK foods in cambridge does not reprimand or discipline there cashiers everytime they are rude to customers.failing us as customers making our experience as shoppers unbearable and not wanting to shop there again because of this kind of behavior...I have no words and am disgusted with this type of service from this cashier and this store.no words left.poor and terrible service and I Wil not be shopping here anymore.thanks