Good Afternoon @Marimar7, thanks for your post on our Community Forums and a very warm welcome to you!
Sorry to hear of the issues you've been experiencing with the landline
Can you tell me when you tried to use the phones in the master socket, have the phones been the only piece of equipment attached to the line when tested?
We'd need to rule out any extension sockets causing any disturbance
Kindest regards,
David_Bn