Charged for Three Wiper Blades only fitted two

We had our Nissan Tiida Serviced with Supa Mac in Durban Road Bellville on the 5th of November 2015, they invoiced us for three wiper blades at R475.00 but only replaced the two front wiper blades, instead of replacing the front two and the rear one.<br> <br> I contacted them twice and they wanted us to bring the vehicle back to them for inspection. This is unacceptable as they where the ones who neglected to do the job right the first time, why do we need to go out of our way to take the vehicle to them so that they can look at the wiper blade. Surely they should come to us as it was them that neglected to do what they charged us for in the first place.