Why can't i receive an incoming call when i'm talking with someone on my iphone?

So i have an iphone 4s. And say someone calls me and i'm talking to them and then someone else calls me.well when the second person calls me i don't get something saying that the second person is calling me like it did before.

Under settings is the option to get notified of a 2nd call and there's a option that sends the person straight to voice mail.

  • Will it show up as a missed call if i call someone by accident for half a ring? So I accidentally called my ex on his iphone, but I quickly realized my mistake and hung up after a half ring. Like you know how when you're calling someone it rings, I hung up after the first riiiing. My question is, will it show up on his phone as a missed call? I tested it out on 2 friends. One iphone 5 and iphone 4. They both told me they didn't get a call. Am I in the clear?
  • Why my Iphone 4s is not displaying incoming call? I have got 4s factory unlocked ios 7.0.4. The problem seems that it is not displaying any call at all but i still hear ringing but nothing displays on 4s. So any help to fix it?
  • Why don't I receive alerts or a notification when I receive a text and I already checked my settings? I adjusted my setting and even put the ringer and notifications on and put the volume and ringer on and I receive no alert, no pop up, alert or notification when someone texts me. Why? This is the iPhone X! I went to the cell phone/ carrier store and they didn't help me. They said to go to the apple store or check the settings. I already adjusted the settings. So what do I do now?
  • Why can't i hear incoming call from skype on my iphone? I use to be able to hear the normal skype ring but recently it is just on silent and says 'incoming call from… ' is this because my phone is on vibrate? But then i want it to at least vibrate when someone is calling me?