Perhaps they found something quite costly and want to repair your Car under the Warranty. You must provide proof of service when asked. You telling them what you did is not going to cut it. This helps contain costs for those of us who do maintain our CRUZE, and keep service records. Some here even take it a step further and purchase a GM Service Contract. If you do not have service records chances are your car won't be approved for any repairs as well, just how it works