Telkom claims the attack on its facilities on Wednesday, which has left thousands of customers without landline or internet services, was an act of sabotage.
The vandalism comes amid strike involving workers affiliated with Communication Workers' Union (CWU).
The CWU memebers are protesting against incentive-based wage increases and other policies.
The telecommunications operator has offered R500 000 reward for any information which could lead to the arrest and prosecution of the saboteurs.
Telkom spokesperson Jacqui O Sullivan says there has always been a close link between industrial action and sabotage in the telecommunications sector.
Listen to the full conversation from The Midday Report with Stephen Grootes: