Good day

In order to answer this question more information will be needed. 

The employer should have drawn your attention to the companies policy. In the policy it should set out what is expected of you. The employer may give permission to see the shopsteward during business hours. If there has been no prior agreement (this includes a collective agreement) then you are contracted to conduct business as set out in your employment contract.

This is not a one size fits all approach, if other unforeseen circumstances arise then it would be advisable to seek help from the union.

kind regards 

LP