Is it possible to change the sound when receiving a message in the iOS and storing it in the settings?

Signed a contract with the Studio, she develops a I need a mobile app.
One of the functions is receiving push messages from the server.
And I wanted the user to the app settings could choose the signal which will receive the message.
The developers have said that it needs this signal to send to the server (the name of the signal sound), because the push message from the server should contain the sound that a message should be displayed. This imposes certain limitations for sending messages - you cannot send all at once, you need to generate each separately with its signal.
Question - is it true? Do not retain the name of the sound in the phone and when a message is received to reproduce this sound? It is about iOS.