I want to try, but i cant think of a way to implement the above, let me clarify in case we did not describe correctly the situation.
So,
Case1: Person A calls Person B, (Person B is free to talk) so Person B gets normally ringed and person A hears normal ringback tone.
Case2: Person A calls Person B, (Person B is busy talking) so Person B now only sees in screen that he has a second call on the back(and maybe hears a tone, device settings) and PERSON A still gets the same ringback tone as Case1.
In my Country when you call someone and he is "busy" BUT HAS enabled call waiting , you get a little tone every other second, or you get a voiceback saying the user you are calling right now is busy, please wait until he picks up.
So how would i differentiate the callflow of Case1 with Case2.
Thank you, i hope i explained it better now.