Employer not settling the expense/ claim approved by manager in fnf

You first ascertain the details and if it is confirmed that the management is manipulating the details you can resort to legal action by first issuing a legal notice demanding the settlement of your dues. 

If there's no response or not complying with the demands made you may file a suit for recovery of your dues.

FNF cannot be correlated to losses in the organisation, issue demand notice for outstanding amount illegally withheld by ex-employer. 

What do you mean by "Now they are denying saying that sale was zero in that month . Claims are of 45000"?
It appears that thee are missing facts. Please post complete facts.
 

Expense for market visit - petrol during the month occured by me were 45000rs for January and February month which was approved by reporting manager but not settled by finance and now HR is saying that I have done zero sale and saying visits shown to site are fake so we will not settled. 

You were advised to send a legal notice demanding your dues, you may consult an advocate and proceed as suggested.

"................. now HR is saying that I have done zero sale and saying visits shown to site are fake so we will not settled" - You may serve the legal notice, as suggested, if the allegations are false.