Lacoste online bad customer service

I made an online purchase last month. I received the order, and the dress didn't fit. I returned the dress, but Lacoste is giving me runarounds with my refund. Every day when I call, they will give me runarounds, telling me that they refunded. I sent them my bank statements to prove that I did not receive any refund. Now they always say they will get back to me and never do. It's been over a month now