Abstract: Techniques for setting up a communication session associated with Evolved Packet System Fallback (EPSFB) are described herein. A fifth generation telecommunications network can implement a server to determine that a user equipment (UE) is incapable of establishing a Voice over New Radio (VoNR) call due to a chipset or other technology used by the UE. The server can send a message (e.g., a SIP380 Alternative Service message) to the UE to cause the UE to begin fallback to another network without waiting for an instruction from a base station in a standardized call flow. The server can establish the communication session for the UE using fewer call flow steps than a number of steps used by a standardized call flow.