We can't tell you that. If you use the same phone for business and personal use, you must have some reasonable method of determining the business use expense, and you must be able to show this to the IRS if audited (it must be on paper or at least able to be printed).
You might use number of personal or business calls, or you might use minutes used for each task, or you might count text messages or determine the data use from your detailed cell phone bill.
