If you're the original owner.. You know your name and birthdate for the account. Aswell as some of your purchases. You can make a ticket or wait for Wednesday and do a live chat with a GM. They always deal ban appeals and hacked accounts on Wednesday, but they don't deal with lost stuff such as missing GP and stuff like that.
You should've get an email confirmation when they changed the account information which you can reset the account back if you didn't make the changes. Check your emails also contact Nexon support. Good luck.