Caller tune function allows the caller to hear the tune which is set by the call recipient.
1. If you are the call recipient, You can modify/remove your caller tune option on [Me] page
> Settings
> Function
> Caller tune.

2. If you are the caller, You can let the call recipient modify his/her caller tune when you feel uncomfortable.
To modify your ringtone:
Enter [Me] page
> Settings
> Notifications
> Calls
> Ringtone

Tips:
After somebody calls you for the first time, he/she may hear your new caller tune.
Ensure a stable network and you and your contacts use the new imo.