No SIM module/slot inside, of course.
There are added on modules you can buy.
I think Onion offers one (OEM.)

A common solution is to get a SIM800L module (assuming your wireless carrier still support GSM/2G),
wiring and powering it correctly:

power needs to be in between 3.7V - 4.2V, no exceptions Tx and Rx direct into Omega2 find/compile the proper library for Omega2

P.S. Omega2 needs a dock, unless you are experienced in makers