Car service

I took my car in for a service in September if not mistaken, I received it back, told everything was in good order. First week of November, it started making scratchy sounds, took it back to them. I was told the brake pads are finished and the disc is now damaged. It made me wonder if the service was done properly because I believe if all of this was happening, they should have inform me to say, the brake pads are finishe, they won’t last me for a certain period. I believe that the disc damage is due to severity of pads damage and it could have been avoided had they assessed the car properly. Now it left me wondering if they had ever done any service on my car at all? Most of the time when I’m fetching the car from the service, I’d be told that the invoice will be emailed to me, and not get it for weeks.