Phone weird dial tone issue and poor call quality.

So my phone when I activate the phone, the dial tone is weird it almost has an old dial up internet connection whirring. When I connect with someone over the phone, the quality of the call is bad as well especially on my end… we have a phone system set up with 4 different remote phones and a base phone, all have the same issue with poor connection and dial tone whirring. Any help would be appreciated, we have already tried restarting the modem.