Date prompt to pick dynamic date values from calender in BI Dashboard is not working.

I have created a BI publisher report with date parameter and created a variable DB prompt with the Presentation variable as same parameter name, after adding both to Dashboard, the Date parameter is not picking correct values as passed, it seems that the issue is in defining BI parameter and henceforth it is not linking correctly to the DB prompt, I have written this SQL query because i have to fetch current month data: kindly help me rectify this if required:

where PAYROLL.paydate BETWEEN trunc(:EFFECTIVE_DATE,'MM') and trunc(last_day(:EFFECTIVE_DATE))

I have already tried below documents and links, but the issue is still not resolved: