Rude manager!

Bought my daughter tea sets from Gateway, 3 days later I brought it back for exchange and the manager said I should produce a proof of payment. Told him I do not have the receipt and he told me to get a bank statement that shows I bought it at their store. Went to the bank printed it out only for him to rudely tell me I won’t get a refund. Now why send me to the bank for a statement if you’re not going to help me! I left the items at the shop as I have no need for them, I just want my money back now!