Comment envoyer des SMS en flottement
// if you couldn't work with flutter_sms, add telephony package in pubspec.yaml
final Telephony telephony = Telephony.instance;
// this method does not need any permission
telephony.sendSmsByDefaultApp(
to: 'target phone number',
message: 'message'
);
// worked for me.
FunnyPointerException :|)