This answer should not be considered specific legal advice, nor does it establish an attorney client relationship. Um, completely innocent, that is not what your question sounds like- you knew you could not get a phone without a deposit and even if your friend let you use her information, if the phone was for you, not her, can still be fraud. If you are charged you will need an attorney, either a public defender or private counsel if you can afford it. Given your question, you will definitely not want to represent yourself.
What a mess. Fraud requires intentional misstatement with the further intent to cause another party to rely on that statement, and due to their reasonable reliance, they sustain damages. There is a very high burden of proof here on the phone company or the prosecutor if it goes that far. I highly recommend that you retain an attorney to review the contract, the facts and the law to see if he can get you out of this.
This answer is provided for informational purposes only. Actual legal advice can only be provided in an office consultation by an attorney licensed in your jurisdiction, with experience in the area of law in which your concern lies.