To clarify - Netflix offers a free month, so you sign up today, cancel tomorrow, but can still watch for the remainder of the month?
If so, I need to go dig out the Netflix offer from my email’s trash can.
When I sign up for a streaming service, I always pay using a gift card, that way I never have to cancel. When I have used up whatever timeframe I have paid for, the service tells me I have to add a payment method or the account will be canceled. It also serves to keep fewer companies from having my CC/bank info. I do the same thing with iTunes and Tracfone.