It depends on where the occupation information is on your work permit.
If the occupation is under Additional Information
You can work in any field. You don’t need to apply to change your work permit. If you have a co-op work permit, your work must be required to complete your study program.
Figure 1. Occupation information under the “Additional Information” section of a sample work permit.
If the occupation is under Conditions or Remarks/Observations
You must work in the field listed on your permit. You must apply to change the conditions of your work permit if you want to work in a different occupation. To do this, you’ll need to apply for a new work permit from within Canada. Select “Inside Canada” to find out how you can apply for your new permit. Include a letter explaining why you need the condition removed from your work permit with your application.
Figure 2. Occupation information under the “Conditions” section of a sample work permit.