Car Service City Silverton

Car Service City Silverton replaced front brake pads on our NP 200 in July. 10 000km later and the brake pad are metal on metal. Took it back to them and they told us it is out of workman's guarantee. Either a very bad product was installed or secondhand pads was installed, but there is no way that, brake pad can be finished in 10 000km. Very unprofessional and bad service.