I received a call from the National Tax Service (1588-2300). Could this be voice phishing?

‌I had a missed call, and just in case, I checked to see if I had any fines, unpaid taxes, or tax refunds, but there was nothing.
That leaves two possibilities.
The year before last and last year, I frequently placed bets at a lottery shop (legal Sports Toto) that I visit often. There were about three times when I aimed for high dividends and the payout amount exceeded 10 million KRW (though I lost it all later ㅠ). Since I didn't have cash on hand at the time, I received the money via bank transfer. Could this be a call asking me to explain those transactions?
What makes this a headache is that the lottery shop has since closed down, so I have no way of finding the owner. However, I purchased everything through legitimate, legal channels, and since Sports Toto payouts are taxed before being paid out, I have already fulfilled my tax obligations. If the National Tax Service claims these deposit records are undisclosed income and demands tax, would I have to personally prove those records (by finding the owner's contact info and obtaining call recordings, KakaoTalk messages, texts, or purchase history)? Or is this something the National Tax Service should investigate on their own without me needing to provide proof?
Another concern is that I changed my phone number earlier this year; is it possible they are calling because of an issue with the previous owner of this number?
Lastly, the representative number is 1588-2300. Is it possible for voice phishers to spoof this number?