Consumer Redressal

I was told that it would cost me 5,000 over the phone. After they picked up I had sent them 5,000 but then they put a bill of 18,500 for my classic 500 dessert storm. If they would have told me earlier, i would have either brought it by train which would have costed me around 5000 again or through Aggarwal Packers and Movers - who are really reputed. Why would I pay 18,500 for a low grade service? My main problem is I was not told that the price would come to this. And I had agreed to pay 10,000 but they are bent on charging the full 18,500.