I only used Netflix from time to time and i would just buy one of these scratcher cards that lasts me a month or two and then i forget about it for a year.
I did this in march or so and saw yesterday that my netflix is still working. I was a bit confused until i saw that they just charge my phone bill to keep netflix running.
My sister said something similar happened to her, where she shared the password but stopped paying but the personwith whom she shared with said something like: they asked me a billing question and they just clicked on "yes" and it appeared on her phone bill too.