Saya tidak mau mengganti kamu (I don't want to change you)
Mengganti can mean replace, substitute, change and they are used interchangeably.
If you don't want to change someone's behavior then " Aku tidak mau mengubah kamu"
If you want to replace like someone's shift or like their position in whatever relationship then (saya tidak mau mengganti"kan" kamu) makes more sense.
More examples
1 Saya tidak mau mengganti baju saya (I don't want to change my clothes)
- Saya tidak mau mengubah penampilan saya (I don't want to change my appearance )
Another thing is when you say dia, it can mean (he, she, it) but at schools we were taught like he - dia laki laki, she= dia perempuan, it =benda/objek.
Otherwise if you just say dia without specifying the person or providing the English translation, then we just assume they are either he/she.
Saya berharap dia suka saya. (I hope she likes me)
Dia berhenti bekerja dan pulang. (He stopped working and went home)
Been meaning to thank you for this comment!!! Awesome truly! Talk in DMs