Two phone CL82207 syst,

Hello @grimalf80 , we will be happy to offer a helping hand with your landline concerns you've been having.

To better assist, we advise you try some of these steps to troubleshoot your home phone.

We would start by checking to see where the concerns are coming from within the home. Here are some steps on how to go about that:

• Check your DSL filters: Turn off or unplug your modem. If the issue went away, then a DSL filter is likely the problem.
• Identify the failed DSL filter: Unplug one filter at a time from the telephone jack (wall). Leave the DSL filter you just unplugged attached to the device. Use another phone and DSL filter on a different jack to see if the problem still exists.
• Test your devices: Plug in all of your DSL filters and devices, one at a time. Perform a test after each device is added. If you still have the problem, it is likely the phone, fax, or other device is defective. Remove or replace that device.

If trouble is not coming from inside, it may be an outside issue. Here are the steps on how to troubleshoot that:

• Locate the Telephone Network Interface. It’s usually located on the back or side of the house.
• Use a screwdriver to open the box. Look for a phone jack labeled customer access jack.
• Unplug the short telephone cord and plug in your corded phone.
• See if the problem still exists. If you:

• • Don’t have a clear dial tone: The problem is with the AT&T network. You’ll have to submit a repair ticket online at att.com/repair or call us. Be sure to tell the repair specialist about the troubleshooting steps you have take
  • Do have a clear dial tone: The problem is inside your home, and you should check for inside issues.

• Unplug the corded phone and replace the short telephone cord. Make sure you close and tighten the Telephone Network Interface cover.

The article we linked above allows you to check your other electronic devices, and also submit a repair ticket if the troubleshooting did not help. We also have the ability here on the community forums, to be able to submit a repair ticket for you. If that is the route you would like to take. We will be here to help with any further  assistance needed.

Lani, AT&T Community Specialist

You may have a line problem that is only affecting one line.  If you have two cords coming into the phone, swap them and see if the error moves to the other line.  If you have a single cord with both lines, you'll need some sort of adapter to switch the lines for the testing.  Unless there are two test jacks at the NID, it would have both lines on a single jack, so you probably would need an adapter to test there as well.

In short, it's probably not the phone itself, but the phone line/service at fault, but you need to test that conclusion somehow.  And, ideally, to take the test to the DEMARC so that it is conclusively either an inside wiring or phone company issue.

On a cordless two handset phone system, both handsets are controlled by the base unit, they are not individually controlled. It's possible one handset has become unregistered from the base unit, try reregistering. Here's the manual this is a single line system. 

OH!  I'm sorry, he said "phone", I read "line."  Duh.

@JefferMC I often do the same thing, instead of reading carefully I skim through and sometimes miss things. I just did it on the topic with the quad wire in the Internet forum. Good thing edit works.