Even if you do that its a simple matter of disconnecting you from ptcl's end.
In other words its a peace of cake to disconnect any modem or restart it since they have control over your modem from backend. That is why ptcl dont need to share username and password of device to its user because they can do settings from any city "Remotely".
My point is they can use anyone's ip/ ptcl connection when ever they want by simply disconnecting the original owner of that ip/Account