Intermittent voice break during phone calls

Hi

I am using iPhone5S and last few days having this problem. During phone conversations, I get intermittent voice breaks. During that period I cannot hear other side nor other side hears me. Other observations:

1. This interruption is for 5 to 6 seconds
2. This is also observed during call making process/ringing. I couldn't hear the ring couple of seconds.
3. I also hear a jumbled up noise during this time
4. This doesn't look like a network issue as it is observed many places I use the phone.
5. I do have other iPhone 4 at home, that works fine on the same network provider.

Kindly suggest any fix for this.