a fake fir sec 3 & 4 dp act (u.p)

Sir, A fake FIR - Sec 3 & 4 dp act, sec 504&506. Allegation - marriage was fixed and girls family gave us 1 lakh rupees in july 2017 and now we are cancelling marriage due to increase in dowry demand. Truth is we just saw girls family in july 2017 and nothing was finalised. My Question is- investigation officer is now making another story that i was in live in relationship for 1 year, but reality is i saw the girl only once in july 2017. In original complaint nothing related to live in relationship has been mentioned. Can fir be modified now to include fresh live in relationship charge, as this is another fake story. Kindly help me.