servicing

i took my car for a service and my car did not hav any problems with brakes but when it came back from service i was told that its left only with 15% of brakes,i then used the car friday afternoon n sunday and sunday afternoon my brakes started having some funny sound and i called Hyundai in alberton n they told me thats because they were finished but im so surprised that why did it happen immediately after it came back from service.i call them but they still told me the same storry which i still dont get it as i feel the is something that they did to my brakes,.i will never take my car there for service ever again