Cell C confirmed to MyBroadband that employees who belong to ICTU have embarked on industrial action.
"This relates to bonus payments made in 2018 for work-related performance in 2017. Cell C is engaging with the ICTU leadership and its members to work towards a positive outcome," said Cell C.
"Plans to minimise disruptions to both Cell C's business and its service to customers are in place. As a business Cell C respects the rights of its unionised employees to take part in a peaceful strike."
No bonuses paid
An ICTU member who was interviewed by eNCA at the protest said bonuses were promised to staff if Cell C met certain performance targets, but these were not paid.
Employees were reportedly promised a 25% bonus by Cell C management.
"We believe we have reached the target… we have worked hard, we need to be rewarded," stated the ICTU member.
The protest action has resulted in the "shutdown" of Cell C's head office, with the protestors blocking the main entrance to the property.
ICTU is reported to have 900 members who could take part in the Cell C protest.
