Download using the Public Key NKX3KE13, download Petit Modem.
Then make a text file, and copy the downloader script to it and save.
Open Petit Modem, select a send speed (the smaller it is, the slower it goes, but will be more stable).
Select RECEIVE FILE SIMPLEX and put your 3DS microphone...
I've owned both iPhone and Androids over the years. Both are just as good, other than Apples higher price. I'm currently on Android, Samsung S21 I think, and very happy with it.