This forum is for people who are using the Samsung smartthings home automation system.
There is an ADT model of the Samsung Smartthings Hub, but it is not the same as the regular ADT systems, it does not use the same equipment, and does not have the same contract structure. It’s also usually installed as a do it yourself project, not by a technician.
It sounds like you have the regular ADT system with the long-term contract, so I don’t think anyone here will be able to help you.
If you asked the question of the technician and were given the wrong answer, that does seem like an issue with the company. You might file a Better Business Bureau complaint, that often gets the company response. Or depending on your state/city, contact your local consumer protection office.
The issue on whether the LED on a sensor lighting up violates the Sabbath or not is one on which different rabbis disagree, so you should also check with your own rabbi to make sure that the guidance you were given applies to your specific situation.
As a general principle, the main panel being turned off won’t solve the problem you’ve described because the battery-powered sensors will still light up their LEDs when the doors open even if the panel is turned off. You have to remove the power from each individual sensor prior to the Sabbath. Which can certainly be done, as discussed in the thread above, but it’s a lot of work each week.
You might also look for a forum for customers of the regular ADT systems and see if anyone has come up with a better answer specific to that equipment.