We use two back end carriers and about to add a 3rd. We do not use Comcast or Verizon. Of the ones we do use, you may have heard of one of the carriers, probably not the other. The 3rd, very unlikely. And no, I'm not going to name them.
No. We're too little to be a financial concern to them. Also, anything they might do would be a bad PR move for them. Then again, I'm sure we'd get more business from the Streisand effect. :-)