This is simply untrue as I've operated. These companies will often take advantage of you if you are not aware. If you utilize a competent SIP trunk provider, they will go to bat for you, and you should never relinquish a number. I realize ILECs present an issue, but again, the law is on your side. Document everything. I will help you for free with this, no problem. Not sure what there is to do post-facto, but I'd raise holy hell.