Hyundai - Unnessary replacement of spare part and overcharging beyond MRP by Kota Hyundai Workshop

I contacted the Kota Hyundai Workshop on **-**-**** for some repair work on my Grand i**. After receiving my car from the workshop at *.** PM on same day I also received the package of the spare part "Control Assy-Heater" along with old replaced part. At this point I came to know that the price of Part charged by the Kota Hyundai workshop was more than the MRP mentioned on the box of spare part. After inquiring about this the service personnel told me that we charged according to the new rate list. This happen to me even after I booked for the same part in **-**-**** on recommendation of the service person in my previous car service.
This is not all after getting my old spare part it was a shock that the old spare part is absolutely fine and is in working conditions. The part that was replaced is not at all damaged and the problem with the AC knob still persist after replacement. The service person was unable to explain me why he changed the spare part.