I have Time Warner telephone service and have 3 cordless phones. One of the phones started displaying a "line in use" message on the display screen. I cannot make any calls from that particular phone but the other two phones work fine as i can both make and receive calls on them. I switched phones on the jack that wasn't working properly and got the same message on the display screen so I'm pretty sure its not the phone but the telephone line itself. Any suggestions?
If you have cordless phones, where are their base station(s) and is it the only thing plugged into the TWC modems line1 and line 2 ports?
do you also have 2.4gHz wireless/ wifi? If these are 2.4 gHz cordless phones there may be interference