Change of private limited company name

Hello All

We are trying to change our company's name to our newly preferred name and our audit firm is asking for Rs 10,000 for it. They say there are extra charges they have to cough up(managing) for securing our new name which they claims he got with great difficultly after convincing(read:manage) ROC . The new name has similar sounding company names in MCA's database but we have a trademark and wordmark registration for the new proposed name. The audit firm for the same name has for a year stalled changing the name because they said its impossible for changing the name to a similarily sounding company name but ever since we have presented our trademark certificates they are claiming that with their good relations with ROC that they have managed to secure an approval for the change. Their stance is that even with a trademark certificate it is highly impossible to get an approval. What is the official fees for changing a company's name? I've googled before writing this post and from what I can gather Rs 500 is the changing fee. 

Any feedback would be greatly appreciated.

Thanks

Raja