The VoIP GSM Gateway is the next big thing in corporate IP telephony. It is intended for businesses that require additional lines of mobile communication. It includes four slots for mobile SIM cards (4,8,16, and 32 ports are also available) and so offers four simultaneous connection channels.

https://medium.com/@gsmgateway972/best-dinstar-32-port-gsm-gateway-device-provider-f79f11756d8e