Nokia c500 mobile phone is on the phone, and others call to remind you. Do you have this function? If so, please tell me how to do it! thank you

If you are on the phone, your mobile phone is not turned off. There will be a missed call display and no SMS reminder. SMS reminder is only when your phone is turned off or there is no signal, someone calls you. It will notify you by SMS, which is a mobile service called communication assistant. As long as it is turned on, this function can be used. Of course there will be a charge. Secondly, if you want a second person to call in the middle of a call, you can know that just set it to call waiting in the call settings.