I am also very frustrated with Coursera. I once recommended this service to all of my co-workers, but now that I feel completely cheated, I would never recommend it to anyone. I cancelled my subscription last month and received a confirmation of cancellation.
"Per your request, your subscription has been canceled and you’ll no longer be charged. Your access will continue until the end of your current billing cycle. Your current billing cycle ends on 12-12-2018 (UTC)."
Today (03 Jan 2019) I received an email stating that they have renewed my subscription (without my authorization) and charged me the monthly fee of $49. I am unable to find any live support or help. Their chat service is a robot who is completely incapable of resolving this issue. I have reported this as fraudulent activity through Paypal and will do whatever I can to blast this all over the internet until I receive some effective support.