Alarm trouble since April 2016. Related to pulse dialing?

We have a Comcast business triple play with digital voice at a small church. We have figured out that our alarm panel has been unable to contact its monitoring service and this has been going on since April (review of phone logs places original failure between April 17 and April 23).The alarm company says the "line is broken," but I have found that all lines have dial tones, and calls can be made in and out on all of them, including both that serve the alarm panel. Internal cabling has been untouched for years.

But today, something clicked in my mind, and I tried to place a call using a phone that can be made to pulse dial (i.e., emulate old rotary phone).  I could not dial out. Tomorrow, I am going to ask the alarm company if the alarm mainboard is trying to pulse dial during its periodic check-ins.

So, here is the question. Could it possibly be that we had pulse dialing available but Comcast discontinued it during the time frame I stated? If so, they didn't tell us, and that would explain why we've had an alarm that couldn't call out for help.

I tried phoning Comcast for support, but the guy I got claimed that pulse dialing works at this address, which is not so.