Not all numbers are portable in all cases. When my fiance and I decided to both move cell carriers onto a third carrier to get a family plan, only one of us was allowed to transfer. No way around it.
Also, it's still basically impossible to transfer a land-line number to a cell number, as they are apples and oranges.
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.
Also, it's still basically impossible to transfer a land-line number to a cell number, as they are apples and oranges.