Hello,
the model you are referring to has two SIM slots.
--> Dual subscriber-identity-module (SIM) support
● Dual SIM provides for high reliability and cellular multihoming support for LTE and HSPA-based networks using common firmware and technology within the same region (only on all -GA and C899G-LTE-JP-K9 PIDs)
The above is an excerpt from the datasheet linked below:
https://www.cisco.com/c/en/us/products/collateral/routers/800-series-routers/datasheet_c78-732744.html
