Faulty kitchen top

We renovated our kitchen about 3 years ago and had our Island fitted with Ceaser Stone top. About six months ago a crack appeared from the corner of wher the gas hob was installed. The owner of the company admitted that he had never seen anything like that before and undertook to replace the top. After numerous calls he turned rude and said that he will do it whenever. We are extremely disappointed with the bad service and would really like to have this problem sorted