Our cordless Panasonic house phones have 'Check Tel Line' displayed on its screen, and whenever I press Talk, there's no dial tone. I've gone around to all the phones to make sure they're on the hook, and they all are. The phones don't need new batteries, and they're only a few months old. Why is it doing this? My mom was messing around with our Internet box before it happened, so could that be the reason why they aren't working? I've searched online, but I haven't found anything useful. Could you please help? Thanks.