In my opinion, call customer support. There's also this link. If you are a native Korean it will be much easier for you, but I'm not sure.
Unless you have a korean phone number, its basically impossible to get a 15+ verified account. If its so you can source raws, you'll be much better off finding someone who can just rip for you thank trying to get verified yourself.
Yeah, it's not impossible. https://receive-sms.cc/Korea-Phone-Number/821025058048 https://quackr.io/temporary-numbers/korea/82105551109 Try these.
Some platforms block virtual numbers, perhaps kakao page is one of them. My bad, I just tried and it doesn't seem to work.
No worries! I also tried the skype number thing but it blocks me from getting them when Im about to pay