Landline Phone Troubleshooting

Hi I live in a rural part of the SF Bay Area And I have Cruzio (Serviced by AT&T) the line has been saying Line In Use and the internet is so slow I can not even load google the line also goes out normally apparently the line is underwater inside a hose and apparently almost 50 years old (The be

"The call cannot be completed as dialed - try again later, OV 6" “The number dialed is not in service please check the number and dial again OV 7” "Were sorry your call could not be completed as dialed please check the number and dial again OV 9" "Were sorry your call did not go through ple

My landline phone beeps when you pick it up to make a call. It says there is a voicemail message and there are none.  How do I get this to stop.  It started happening after a power outage?

Have a problem with static on our landline, after disconnecting the house from the outside line and determining it is not in the house, I went through the process for asking for a repair. I was given a time