How to stop Iphone 4s text sound from playing when I'm on a call?

I have an Iphone 4s and I have tones set for text messages. I like to be notified by sound when I receive a new text message. However, the annoying part is even when I'm on a call the sounds still plays in my ear when I receive an incomong text message. I have to inform whoever I'm speaking with not to talk b/c I can't hear them over the sound playing. The other party does not hear the sound. It gets really annoying if I'm on a conference call for work.

Mu husband and mother both have the same phone but are not experiencing the same problem

There isn't a setting to where you can silent it JUST for when your on a call.

I had the exact same issues but what i did to help was, everytime i got on a call, i would hit the switch on the side of my iphone that makes it vibrate. Now when i'm on the phone it'll just vibrate a little but won't bug me at all. Takes a while to get used to keep on putting it on vibrate but it helps.

There has to be something in settings that you can click to turn it off, especially since someone else has the same phone and that doesn't happen to them. That means there's an off switch somewhere. Try going into Settings >> Notifications >> scroll down to Messages >> scroll down to Repeat alert >> click never
i haven't tested it out to make sure this works but it's worth a try
if not, look around in settings