You do have a couple of options.  First you could meet with the principal and explain what happended and why you daughter used her phone.

Second, you could file a formal appeal of the school employee's decision, taking this through the school system process.

Here is the big issue for you to think through.  If there is an expressly written policy about using cell phones and consequences for this use, your appeal is likely not to be successful.

In other words if there was a clear written policy, an appeal may be very difficult to change the original decision.

One of the reasons for not allowing cell phone use is there have been numerous situations where students have used their cell phones to share with other students the questions on a test.

Good luck.