Not negotiation experts

My daughter is an au-pair and Corporate traveler booked her flight to Amsterdam and her return ticket. In July 2017 we had to change her return flight to December as it was booked for August 2017 for some other reason I don't know. Travel agents may put in a service request for these type op passengers but they didn't do that I had to pay R1000+ to change the date of her flight in July to the travel agency. In July KLM changed their check in baggage allowance to 2 check in bags per passenger but our baggage allowance was not changed it remains 1 bagg only. I queried KLM and they reffered me to the agent blaming them for booking 1. Corporate traveler blame KLM and just keep to the story that KLM has rules and does not allow changes. Why work through an agent if they do not want to assist you at all, I don't buy the fact that KLM and they can't negotiate surely Corporate traveler has been doing business with them for a long time and give them a lot of business, the au-pairs alone from Nedsa is very good business and we all work through corporate traveller.I honestly feel in July they must have taken it up with KLM and see to it that we get the best service which will be the extra check in bagg for my daughter. Why should we be penalized because we worked through a travel agent- not fair and not good service.