Best answer by Maryam
So this course must be a part of a Specialization as you're talking about subscription. I'd like to divide my answer into 2 sections:
1- Before completing a course
If this is an entire Specialization (and you intend to do the whole Specialization), you'll be charged every month until you get your Specialization Certificate. If you want to do a single course in a Specialization, you'll need to cancel your subscription after completing the course because, unlike the first case, your subscription will not be canceled automatically. If you cancel your subscription before completing it, you'll no longer have access to paid materials such as quizzes. For more information, please take a look at this Help Article: Coursera subscriptions
2- After completing a course
After completing your course(s) and getting your Certificate(s), you can always go back to the materials and review them to refresh your memory.
I hope these help.