In South Africa, an employer cannot force you to sign a new employment contract.

However, there are some important considerations:

1. Consultation and Agreement: Any changes to your employment contract should be discussed and agreed upon by both parties. Employers typically need to consult with employees and obtain their consent before making significant changes to the terms and conditions of employment.
2. Reasonable Changes: Employers may propose changes to adapt to new business needs or legal requirements. If the changes are reasonable and necessary, it might be in your best interest to consider them.
3. Refusal to Sign: If you refuse to sign a new contract, your employer cannot automatically terminate your employment. However, they may take further steps, such as negotiating with you or, in some cases, initiating a retrenchment process if the changes are crucial for the business to survive or if the changes are an inherent requirement of the job.

I would suggest that you take the new contract to a labour lawyer to assess the new terms and condition before you sign it.  If you sign it, you will be expected to go along with the new terms… so beware of signing something you do not agree with..