No sound is coming from my iPhone 6 speakers

Hello--

As of about 10:00 PM on Saturday night (Dec. 5), my phone stopped making any sounds. No text message sounds, no keyboard click noises, music doesn't play through the speakers, etc.--nothing. I didn't do anything to the phone to cause this (drop it, etc.); it just spontaneously stopped making noise.

I've done all the checks to make sure I don't have volume turned off:

• silent mode is not on;
• "do not disturb" is not on;
• volume is turned all the way up.

(there is no "user error" issue here!!)

The only way you can hear anything is if the earbuds are plugged in. I just got this phone in August so I am hoping it is not already defective. Does anyone have any suggestions as to what might be wrong and how I might be able to troubleshoot it/fix it at home (vs. taking it in to the Apple store)?