Hi

Follow the instructions here:

If your headphones don't work with your iPhone, iPad, or iPod touch - Apple Support

Your post doesn't make sense to me.

iPhone 6s plus earpeice volume low

can't even make a call without using the headphones. any ideas?

The first statement indicates that the volume is low when you are using the earpiece.

The second statement indicates that you can't make a call without the earpiece, so by my deductive reasoning, that means that your speaker volume isn't working properly and you need to use the earbuds in order to hear.

Can you clarify?

If your issue is that the volume from the iPhone is too low, follow the steps here:

If you can't hear a person on a call or voicemail or if the sound isn't clear on your iPhone - Apple Support