poor service

I paid ck autor spares for the right rear airshock for my mecedes e500 and before i paid in the money i called in to make sure they have it. The person who was helping me was Andy he told me they do have. It was not the first time working with them so i trusted them I deposited the amount of 3500 23/03/2018 and fexed the deposit slip to them. A week latter they told me that they do not have it in sock but they will have it in a weeks time. Its almost a month now i havent received my money back as they promised to refund me. Ive been calling them and sending messages to them sometimes they answer sometimes they ignor my messages. Till now i havent recived my money back and i need it. They keep on promising me my refund but its been too long now