I am stuck here again waiting for AT&T to fix the phones.
They want $55 an hour if it is my fault.
It's really simple actually.
All you need is a standard corded phone.
Go to the network interface device.
Plug in the cord phone.
If there is dial tone, you have inside wiring problems.
If there is no dial tone, it's their equipment.
The phone company is only responsible for service UP TO THE NID.
Beyond that is your problem.
You can hire a local telephone guy to troubleshoot from the NID to your phone's handset.
On new installs, it's often the NID or the phone company's problem.