missed call from this number

hi may i know is this?

this number was calling me more than 20 times a day.

and you cant avoid to answer since my number was issued for business inquiry for customers

outside the country where im currecntly working.

also from +2399883021

+2399883021   This calla are from "Republica Democratica de São Tomé e Principe" a Portuguese-speaking island nation in the Gulf of Guinea,  west Africa coast eland, not from US. +239 is country code , not US area code. I receiving this call from time to time, but I do not replay or call back, as it is scam call.