If you come to a unilingual Service Canada outlet and you speak to the person behind the counter in French, let's call her Ms. Gaudreault, she will be ready, willing and able to speak to you in French. However, she will also make sure to tell you that you are in a unilingual service centre and to show you the place or the telephone number where you can access bilingual service.
She will tell you that simply because she does not have all the support that she needs to provide you with French language service equal in quality to the service that would be provided by someone who has been trained to provide service to the public in French. Your questions might have to do with employment insurance or with the Canada Pension Plan. The reason is simply that she does not have all the necessary support, she is not set up in the same way as an employee at a bilingual service centre.
However, clearly, as a matter of courtesy, she will speak to you in French, she will help you in French, she will provide you with the French language documents that she has available. In addition, she will also be expected to tell you where the nearest bilingual Service Canada outlet is located, or the telephone number you need to reach it.