monitoring of minutes being used vs. The monitoring associated with the calls being made

Section 1.5 of the Wireless Customer Agreement;

1.5   How Does AT&T Calculate My Bill?

Usage and monthly fees will be billed as specified in your customer service summary or rate plan information online. If the Equipment you order is shipped to you, your Services may be activated before you take delivery of the Equipment so that you can use it promptly upon receipt. Thus, you may be charged for Services while your Equipment is still in transit. If, upon receiving your first bill, you have been charged for Services while your Equipment was in transit, you may contact Customer Care 1-800-331-0500 to request a credit. Except as provided below, monthly Services and certain other charges are billed one month in advance, and there is no proration of such charges if Service is terminated on other than the last day of your billing cycle. Monthly Service and certain other charges are billed in arrears if you’re a former customer of AT&T Wireless and maintain uninterrupted Service on select AT&T rate plans, however, if you elect to receive your bills for your Services combined with your wireline phone bill (where available) you will be billed in advance as provided above. You agree to pay for all services used with your Device.

AIRTIME AND OTHER MEASURED USAGE ("CHARGEABLE TIME") IS BILLED IN FULL-MINUTE INCREMENTS, AND ACTUAL AIRTIME AND USAGE ARE ROUNDED UP TO THE NEXT FULL-MINUTE INCREMENT AT THE END OF EACH CALL FOR BILLING PURPOSES. AT&T CHARGES A FULL MINUTE OF AIRTIME USAGE FOR EVERY FRACTION OF THE LAST MINUTE OF AIRTIME USED ON EACH WIRELESS CALL. UNLESS OTHERWISE PROVIDED IN YOUR PLAN, MINUTES WILL BE DEPLETED ACCORDING TO USAGE IN THE FOLLOWING ORDER: NIGHT AND WEEKEND MINUTES, MOBILE TO MOBILE MINUTES, ANYTIME MINUTES AND ROLLOVER, EXCEPT THAT MINUTES THAT ARE PART OF BOTH A LIMITED PACKAGE AND AN UNLIMITED PACKAGE WILL NOT BE DEPLETED FROM THE LIMITED PACKAGE. Chargeable Time begins for outgoing calls when you press SEND (or similar key) and for incoming calls when a signal connection from the caller is established with our facilities. Chargeable Time ends after you press END (or similar key), but not until your wireless telephone's signal of call disconnect is received by our facilities and the call disconnect signal has been confirmed.

All outgoing calls for which we receive answer supervision or which have at least 30 seconds of Chargeable Time, including ring time, shall incur a minimum of one minute airtime charge. Answer supervision is generally received when a call is answered; however, answer supervision may also be generated by voicemail systems, private branch exchanges, and interexchange switching equipment. Chargeable Time may include time for us to recognize that only one party has disconnected from the call, time to clear the channels in use, and ring time. Chargeable Time may also occur from other uses of our facilities, including by way of example, voicemail deposits and retrievals, and call transfers. Calls that begin in one rate period and end in another rate period may be billed in their entirety at the rates for the period in which the call began.