Why my account get hack,and how do i get my vp back?

please help me , I just logged in to the game after a while and after I returned my vp then was around 5000vp is now reduced to 1408vp
I don't know who used my account when it wasn't active, I never shared any information about my account,please give me a solution.
I feel very insecure because I paid around Rp. 500,000 idr+i confuse why my acount can get hack
What should I do now?