There is no 'none' option for billing, why?

Every time I try to download a free app, or update one of my apps it tells me to update my billing information, so I do so and everything is upto date. But when click done it tells me I can't use this card, is not a credit card but a debit card as im only 14 years old. So I want to take my card off my billing information, but it doesn't give me an option for 'none' like its suppost to. Therefor I am unable to use any of my apps, as they all need updating. Please someone help me. Thank you