Quiet During Calls

I'm not sure where to ask about this, so I figured here would be best.

Anyways, while i'm in a call with someone, i normally use my iPhone earbuds. I previous had the iPhone 5C, and the person I was communicating with heard me well enough that a whisper was audible. However, I upgraded to a 6S Plus a few days ago and when i contacted the same person, using the earbuds i was given, hearing me was more difficult to the point my voice would sound audible then suddenly just cut off. I figured it was because i was whispering (as these calls are taken at night and i don't wish to disturb anyone), however i used to whisper with my previous phone and i was heard perfectly fine.

Does anyone know what this issue is? Is there a setting i can fix on my new phone so i can be heard more clearly even with a whisper? This would be greatly appreciated if someone could explain.