Oxford's telephone network has been thrown into chaos after half of the city's NTL lines stopped working on January 15.
Engineers said a severed cable was the cause of the problem, which started at about 10.30am.
The underground electricity cable in Abingdon Road caused damage to an NTL cable, leaving 900 customers unable to make or receive calls.
Southern Electric secured the high voltage cable during the afternoon before NTL started work repairing the damage.
Jennifer Mcgregor, of Southern Electric, said: "Our electricity lines have been in place for many years.
"Often when contractors put new cables on top this causes damage to ours and this leads to problems like this."
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