L C A

On Feb 28 2014,I bought a 2006 Dodge Charger. On theTest drive I noticed Rattling on the. I returned to Lca auto wholesalers,told the seller the problem. He told me to bring it back the next day to be fixed. I return the next day, and the seller told me to return on a Wednesday. Between Friday and Wednesday. We noticed service engine soon light. We told them about it they said the would fix it. The following Tuesdays I went to pick up the car and the rattling noise is not as bad as it was, and the service engine soon light was off. The next day the service engine soon light was back on. I have taking the car to LCA AUTO WHOLESALERS a least 6 times to get whatever is making the service engine soon light come on get fix. This has been going on for 30 days now. Please someone help me.