SIM Card?

I have a relatively new alarm system that was installed in a new construction home in 2016.  My contract is coming up for renewal and so I started looking at DIY solutions like Abode and SimpliSafe.  While researching I found konnected and like the idea of leveraging the existing alarm infrastructure and not having to worry about batteries.  My current system uses cell technology for its communication.  If I go with konnected, I’ll have to purchase a SIM, therefore, what company do you guys use for the SIM service?