This option is very important, when you call someone at the same time he talking the phone tell you that person is in waiting.
You can vote in the following link to update this option or at least come with windows phone 10
https://windowsphone.uservoice.com/forums/101801-feature-suggestions/suggestions/5780265-call-waiting-message-please
Make change
You can vote in the following link to update this option or at least come with windows phone 10
https://windowsphone.uservoice.com/forums/101801-feature-suggestions/suggestions/5780265-call-waiting-message-please
Make change