I purchase a motor Grundfos 2HP smart sub through ...

I purchase a motor Grundfos 2HP smart sub through authorised distributor 2-3 years back. The motor is fully rusted outside and the motor lifting hooks dissolved in metro water.
Service is very very poor. The service people from Grundfos saying it is only scaling not rusting. Then where is the motor lifting hooks. They are simply saying the castor part of the pump gets dissolved in water. Then why should we buy Grundfos immersible water. We can buy local one. The people in grundfos service is non-cooperative.