Siri unable to hear me

For the past 2 years Siri was fine, I could have my phone 20 feet away call for Siri and she would respond. But a few days ago she unable to hear me as well. Now I have to be within 5 feet yell "Hey Siri" for a response. I found out the phone switch the microphones so now it using the front facing mic (ear piece speaker grill). How can I get Siri using the bottom microphone again?