Dallas Cell Phone Ban and the 1st Amendment

The Dallas School Zone Cell Phone Ban contains the follow defense to prosecution-

(d) It is a defense to prosecution under this section that the person was:
(1) operating an authorized emergency vehicle and using the mobile telephone
or mobile communication device in the course and scope of the person’s
official duties;
(2) using the mobile telephone or mobile communication device to:
(A) report illegal activity to a law enforcement agency;
(B) communicate with an emergency response operator, a fire department, a law enforcement agency, a hospital, a physician’s office, or a health clinic regarding a medical or other emergency situation; or
(C) prevent injury to a person or property;

Instead of banning all cell phone speech, the government is simply banning unnaproved speech. It’s ok to call the cops, but not to call your wife.

The First Amendment does not come up often in my law practice. My Con Law class is a distant memory.

My question for law students and Con Law scholars-
Does the first amendment apply to the cell phone ban? If so, is this unconstitutional?

I wish the 9th and 10th Amendment would protect your right to use a cell phone in your car. However, those amendments have been repealed through neglect.