Cashier changing for more than one packet

When to the store and did my shopping and got to the till to make payment and then I asked the cashier for a packet of cigarettes and then she called the supervisor 3 time just before she came to the cashier and then I made payment just for me to see that the cashier changed me for 2 empty packet and came me one ,when asked she said that it must be a mistake and she would refund me and then I when and spoke to the manager and asked how many customers a they changing like this and she said that she would give me a refund and I said no and walked out