I went for my first 10000 kms (actual mileage 6300kms after 7 months usage) brakes service for my 2017 Altis 1.6L facelift. After the service, I started hearing a loud clunking sound when hitting the brakes in reverse. I returned to 3s dealer and asked him to check it but the reply was, "it's all normal." However, they re-checked everything but the sound is still there and is unusually loud but the mechanics insist it's normal. I'm really confused. Would appreciate your input on this.