First link her account to a pre-pay card. Seriously consider taking the phone for now. give her a Pre-paid phone to text. It's not a punishment it's to protect your finances. Have you talked to her teachers about why her grades are so bad? Does her school have a site parents can see the grades? Is she misbehaving in school? All these need to be taken into account before deciding. Does she have a lot of friend's? do you have other children? their ages? Is your house child proof?