The word “topia” is actually a synonym, often used as a suffix, for a geographical region. You will notice that the title of the album this track (“Topia Twins”) is derived from is relatedly titled “Utopia”. But...
Concerning the title of this song, the word heyy is apparently some type of internet slang that’s an abbreviation of ‘hey you’. In the chorus of this song, Lil Baby does not use it in such a fashion...