I installed a ppp connection and everything is working correctly. My problem is: how do I send AT commands? I want to test several things, such as send sms or put the module in sleep mode.
I tried solutions like the ones shown here. However I don’t know which device I should choose (in the example ttyACM0) and I tried a few but it gives the error:
serial.serialutil.SerialException: [Errno 16] could not open port /dev/ttyUSB3: [Errno 16] Device or resource busy: '/dev/ttyUSB3'