Try given code. Check your switch value is in left or right, I'm consider your switch varible is yourSwitchIsRightSide.
MFMessageComposeViewController *messageComposer = [[MFMessageComposeViewController alloc] init];
[messageComposer setMessageComposeDelegate:self];
// Check The Device Can Send Text Messages
if ([MFMessageComposeViewController canSendText]) {
[messageComposer setRecipients:[NSArray arrayWithObjects: nil]]
//yourSwitchIsRightSide should be bool value
if(yourSwitchIsRightSide){
[messageComposer setBody:yourRightMessageBodyText];
}
else{
[messageComposer setBody:yourLeftMessageBodyText];
}
[self presentViewController:messageComposer animated:YES completion:NULL];
} else {
// Need to add an alert view
NSLog(@"TEXT ISNT WORKING");
}
}