This is an increasingly common situation and one that schools can be very hard-headed about because of the ubiquity of e-devices that make cheating so easy. It sounds as if you have been referred for administrative charges of violating academic integrity standards, but it is not clear whether you are facing discipline (expulsion) or just the zero for the exam. If the zero, that is probably the best that you can hope for. If expulsion, this may be worth hiring an attorney and making a formal appeal of the school's determination and even testing the school's determination in court. Warning: school discipline cases are not a level playing field. Your burden is to persuade the school that its trusted faculty member is wrong, biased, etc. Very tough factual burden. Unless the phone has some stored data feature that can be used for demonstrative evidence to prove the pages that had been accessed and the dates/times, then it is your word against the professor's and that is a very very difficult case. If you think the stored data will prove you right, then you may want to retain an expert to examine the phone under school-approved controlled conditions and make a written independent report to the school.
In all events, this will be expensive and you are at substantial risk. Word needs to get out to all college students: never take a phone or e-device out of a backpack or other closed container during an exam. Never, for any reason. This is at least the 12th case on exactly these facts that I know of in the last 8 weeks.
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From the other side of the country, I would agree with Ms. McCall that universities are increasingly disciplining any potential student cheating. With electronic devices, it is exceptionally easy to cheat in various ways. Furthermore, where it is a "he says;she says" case without any other objective evidence to the contrary, university disciplinary boards will find against the student where the prosecuting witness is the class professor.
Occasionally, the professor will allow the student to retake a similar exam (in a controlled setting) on the same material to see if their knowledge is essentially the same. If so, then the student gets a grade. If not, then the "ax falls".
I would add to my colleague's response that you should be sure you were not violating school policy by having the iPhone in the room in the first place. If not, your best best is to proceed through the schools appeals or grievance procedure.