Terrible customer service

Terrible service received at Builders decor department. I ordered blinds from them and they mixed the length and width measurements and did them visa versa. Upon return to the shop, i was told I cannot return the blinds. The staff denied having done the mistake. After several back and forth with them, I was told that if they make a mistake it will be deducted from their salary. There is obviously no incentive for them to admit to a mistake if there will be a deduction to their salary. Shocking. Now they expect me to pay again for a mistake they have made - extremely terrible customer service. I am horrified