My daughter is Anastasia (Anastasiya), nickname Stasya. We are a bilingual Russian-English family. The name Stasya is pronounced /STAH-sya/, or sometimes /STAH-zya/, but NOT /STAY-sha/. It has the same pronunciation pattern as Nadya, Katya, and Yulya. Stacia/Stasia can be /STAY-sha/ or /STAH-sha/, as well as /STAH-sya/, /STAH-see-ya/, and /stah-SEE-ya/.
https://ru.wiktionary.org/wiki/%D0%A1%D1%82%D0%B0%D1%81%D1%8F