The company, in which the government owns a stake of about 40 percent, plans to also outsource 260 roles.
"We have made important progress on our turnaround in the past two years but we still have a lot to do," said Telkom Group Chief Executive Officer Sipho Maseko in a statement.
Trade union Solidarity said it was "aggrieved" by the retrenchment notice and will negotiate for the survival of as many positions as possible, the union told Reuters.
"We will always fight tooth and nail to ensure minimal job losses," Solidarity union media relations officer Francois Redelinghuys told Reuters.
Telkom is nearing the end of the first phase of a turnaround strategy that includes cutting jobs, outsourcing services such as telephone directory printing and selling some properties in a portfolio whose size is slightly larger than Luxembourg.
Telkom's share price, which has climbed by 300 percent since Maseko took the reins two years ago, was up 0.9 percent at 53 rand by 1225 GMT.