Suspicious servicing and billing

We took our Jaguar X-Type in for servicing. Before reaching the service centre we had checked the car for oil leaks, water/coolant leaks and found it to be working fine with no leaks whatsoever. After giving it in for servicing however, we were told that the coolant holder broke and all the coolant leaked out. This is very very suspicious to us. At the least we want this to be investigated thoroughly. We are not willing to pay the ridiculously expensive resultant bill!