Depends on your version of Callmanager and how you have got them configured.
Early ATA configurations were setup as H.323 endpoints. The early versions of code were especially bad for the problem you are describing. I think release 2.15 or better was much better.
Later ATA configurations using Skinny were even better, (I would recommend using Skinny) when possible, If you have Call Manager 3.1x or below you will manually have to update the code from the horrible Kamodo voice menu, by pressing the button on the ATA, and entering the DTMF codes from the new image upload instructions.
Later versions of Callmanager support the TFTF image approach for the ATA and you should be able to find the version with the other supported devices
