Very disappointed

I've been taking my car for service to Volvo Auckland Park, for the past 7 years. I've been very happy with their service until recently when something that has sentimental value to me was ****** from my car. I did inform them and they promised to contact me once they've done some investigation. A month later, nothing has been done and nobody got back to me. I'm wondering whether to continue with their service or tae my car somewhere else.