Used my car for personal journeys while it was parked with them!

I have used Klipkop Car Care for years and THOUGHT there never was a problem. Last time they had my car in their care I happened to see in my Discovery Drive app that there had been several events of speeding while they had my car. I then obtained a more detailed report tracking my vehicle on the dates in which I was away and it turns out not only did the driver speed in it, he also took it to the local high street to 'buy dinner' and then to the casino where it was parked until 11pm! When I brought this to Klipkop Car Care's attention all I got was an apology and the assurance that they had given a written warning to their driver in question. I will certainly never trust them with my vehicle again!