Yes, It's possible to identify the origination of call whether it is national or international. I also faced the same issue. A 14 digit number called me several times in the past few weeks and I didn't pick up that call because that's an international call. My friend would suggest me to visit
https://www.reversesouthafrica.com/ and feed this number to the input text. After feeding this number I identified that callers. As you also facing the same issue than just take a look at the above-mentioned link. The team member of this website will help you to know all the information about that person.