Operating system name and version: Ubuntu Linux 20.04
Version of smsd: 3.1.21
Smsd installed from: package repository (apt in Ubuntu)
Name and model of modem: Huawei e3372 4G LTE USB modem
Interface: USB

I have installed smstools and have followed this article to set it up. But whenever I try to send SMS to a valid phone number, I can conclude that it does not get sent because the messages end up getting stored inside the failed folder, and this is the status of the smsd.log file:

Is there anything wrong with that article? What mistake am I doing?