Western Union / Agreement — no payment in front after my confirm fee

the western benin republica contact me after some person from ministry of finance call contact me that i received my inheritance mandate from imf and in this country i have values of deposite in certificate.
And they said i must confirm and pay just one time for re instatement fee to this western..after i pay as their requested, they sent me that i must to pay for my certificate, i said let sending me my first inheritance payment so i will pay this certificate. how i must to do ? because the people on there many time ask for payment bit by bit until tired and then never provee it.