Telstra services are down in the South Western suburbs.
A third-party contractor accidentally cut 3 optical fibre cables while digging in Clarence Park last night.
4,500 ADSL services are off-line from Unley to Marion and down to Brighton, while 9 mobile phone towers are also not working.
Apparently no fixed-line services have been interrupted.
Telstra expects everyone to be gradually brought back-on this afternoon with full restoration by later today.