Hey!
Does alarm.com still make a SEM for the concord $? If so does surety sell it?
The Concord 4 and Concord cell modules have been discontinued, however Alarm.com still sells an LTE upgrade module to replace the cell board of any existing Concord commmunication modules. Look for the CD-410-US-VZ-LTEUP, but that requires an existing communicator.
Do you already have a cell module connected to the system or is there no communicator? If there is no communicator one would be needed, and would likely need to be purchased second-hand. I am not aware of new ones being sold.