Motus mazda select Cape Town dissapointing

I recently took my Mazda cx5 to motus select cape Town to fix a wiper sensor issue, when collecting the car I noticed a dented chip on my passenger door which I definitely know was not there when I dropped the car off. I was told by the service manager that there is no proof that it happened at the workshop and that's what the policy says. Even though there was no car inspection done by them that day which they did previously when I was there. As a new Mazda owner this is quite dissapointing and hoped to be treated better as the customer.