Bad service - actually no service

Ordered a floor lamp on 13th July and it arrived on 4 August and after setting it up we discovered it didn't work. phoned returns at Builders and the person who answered assured me it would be exchanged for a new one by the next week. Nothing happened. I have phoned at least 8 times and each time the person says they will sort it out and phone you back to let you know of the progress. only 1 person phoned back and she didn't sort it out. Why do they call that section customer service when there is no such thing. to date have no idea where the new lamp is and if no feedback going to cancel this order. I will never order from them again and am completely put off buying on line.