Calls going silent

I have been experiencing this problem with making some phone calls where it connects to the line I am calling, but it goes silent. They can hear me, but I can't hear them. I have found that it usually depends on who you are calling. I just did a test with a friend's cell phone and a land line. I called the land line 10 times in a row and there is never a problem. But when calling my friend's cell phone, it is random. Would go silent the first time, then be ok the next 2 times, then silent again, and so forth. Also, my friend's cell phone is set so that it only rings one time, and then the voice mail picks up. I know this from looking at the top right of the phone screen where it says "Dialing", and when the call connects, you will see a time counter. When the time counter is running, it is still silent.

I wiped the phone app cache and system caches, but the problem still occurs.

Any ideas why this is happening?