Shell doesn't care about their consumers

I stop at the specific site every morning for 2 Redbulls and cigarettes. Yesterday afternoon a friend bought cigarettes for me but unfortunately it was the wrong brand. This morning as per usual routine I stopped at the same garage for the usual items but instead wanted to exchange the incorrect cigarettes for my usual brand. It was 2 sealed packets and more expensive than what I wanted to exchange it for. I didn't want the change I just wanted to exchange it. The cashier was very rude and arrogant and told me that if I didn't have a slip she cant help. The cashier then called the Manager and she too was very rude. I explained to her that I don't want change - she told me she won't help if I don't have a slip - I mean who keeps a garage slip and if the product was damaged or compromised that I wanted to exchange I would understand but it was sealed packets. I will drive an extra few kilometers but I won't stop at any Shell garage ever again. They don't respect or care about their consumers.