Netflix problems?

About 1 month ago I still had Netflix on my phone. Whenever I paid for the mobile phone subscription, the Netflix amount per month was also on it. However, I had certain problems because my cell phone bill was always way too high (not because of Netflix). Then I decided to simply block all things that can be paid for with a cell phone, including Netflix. Now I want to log into my sister's account but it doesn't work. It always stands to choose a new payment method, even though my sister owns the account. Does anyone know what to do.

Choose a new payment method. You can read it here.

But it's my sister's account. Usually you can just sign up. It's your account.

Apparently she didn't pay. Ask her.