Listening to the Russian pronunciation of Oksana on Forvo (
https://forvo.com/word/%D0%BE%D0%BA%D1%81%D0%B0%D0%BD%D0%B0/#ru), it simply sounds like Aksana to me (I'm Polish). Perhaps people from Uzbekistan, Kyrgyzstan etc. also hear Aksana rather than Oksana.