Magento 2 remove billing phone

I'm not sure about previous versions but in Magento 2.2 you can go to

Store > Configuration > CUSTOMERS > Customer Configuration

Then go to the Name and Address Options tab on the right and look for Show Telephone and select your option. (No) (Optional) (Required)

It's set to Required by default.

After facing the same problem, i found a thread on the official git. Dated from August 2015...

And someone posted a proper solution

Incredible complexity for just doing that...