The phone needs to be turned on at all times and the app running for the SMS gateway to be operational.
If the phone is turned off or the SMS Gateway app is paused on the phone then SMS messages may not send or receive correctly.
We do not recommend keeping the phone on charge at all times.
If you have them permanently plugged in we recommend that you have a timer to turn on and off in order to power cycle the charge.
Please see the installation instructions for full details and correct setup.