"Go Phone" overcharge for minutes

I have the $ .25 minute plan. After every call there is a prompt that gives the amount charged for the call. At least once or twice a day I am charged for more than the amount of the call duration; i.e. a 45 second call charges $ .50.
I check against the 'call times' so I know exactly when I have been overcharged. I have called Customer Service twice - each call with a supervisor that lasted over 20 minutes. They have added 15 to 20 seconds onto each of the calls in question and tell me I need a new to purchase a new phone from them because it is not recording the minutes correctly. I don't want to sink anymore money into AT&T and will be purchasing a Tracfone once these minutes are up (which should be quicker than expected due to the double-dipping.)