I think you've diagnosed the problem yourself - a fault or general deterioration of the wiring/socket in your office has caused the ADSL connection to fail, although replacing the filter is probably the first thing to try.
Samsung Galaxy S8 review
1995-2015: How technology has changed the world in 20 years
What’s happening in VR right now: From psychedelic art to combat therapy
Siri not working? Try these troubleshooting fixes
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.