When Netflix Nigeria website launched in January 2016, Nigerians were allowed to sign up for free Netflix account. I signed up for mine too and I watched Netflix movies FREE for 30days without paying for NetFlix subscription.
I created my NetFlix account using my iTunes account and after I completed my NetFlix registration, the GTBank MasterCard linked to the iTunes account was not debited. In fact, it was not debited throughout the free trial.
So, you can go ahead to enjoy the free Netflix trial without fear of been charged but ensure you turn off NetFlix auto renewal to avoid been charged automatically at the end of your free trial.