EG25-G falls back to 3G when try to make a call

IoT Modules LTE Standard Module
1

I have a EG25-G modem with described problem. Could you please help me? Below I describe what I did already:

AT

OK
AT+QCFG="ims"

+QCFG: "ims",1,0

OK
AT+QCFG="ims",1,1

ERROR
AT+QCFG="ims"

+QCFG: "ims",1,0

OK
AT+CGDCONT?

+CGDCONT: 1,"IPV4V6","","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 2,"IPV4V6","ims","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,0
+CGDCONT: 3,"IPV4V6","SOS","0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0",0,0,0,1



OK
AT+QMBNCFG="list"

+QMBNCFG: "List",0,1,1,"ROW_Generic_3GPP",0x0501081F,202112292
+QMBNCFG: "List",1,0,0,"VoLTE-ATT",0x0501033C,202105171
+QMBNCFG: "List",2,0,0,"hVoLTE-Verizon",0x05010141,202111151
+QMBNCFG: "List",3,0,0,"Sprint-VoLTE",0x05010205,202010201
+QMBNCFG: "List",4,0,0,"Commercial-TMO_VoLTE",0x05010505,202112101
+QMBNCFG: "List",5,0,0,"Telus-Commercial_DO",0x0580F601,202105061
+QMBNCFG: "List",6,0,0,"Commercial-SBM",0x05011C18,202004211
+QMBNCFG: "List",7,0,0,"Commercial-DT",0x05011F1C,202201041
+QMBNCFG: "List",8,0,0,"Reliance_OpnMkt",0x05011B38,202003251
+QMBNCFG: "List",9,0,0,"TF_Germany_VoLTE",0x05010C1B,202004151
+QMBNCFG: "List",10,0,0,"TF_Spain_VoLTE",0x05010CFA,202106171
+QMBNCFG: "List",11,0,0,"Volte_OpenMkt-Commercial-CMCC",0x05012071,202201063
+QMBNCFG: "List",12,0,0,"VoLTE_OPNMKT_CT",0x050113FC,202201063
+QMBNCFG: "List",13,0,0,"CU-VoLTE",0x05011508,202201063
+QMBNCFG: "List",14,0,0,"Telstra-Commercial_VoLTE",0x0580079E,202112221
+QMBNCFG: "List",15,0,0,"Commercial-KDDI",0x0501071D,202011192
+QMBNCFG: "List",16,0,0,"Commercial-DCM",0x05010D17,202111091
+QMBNCFG: "List",17,0,0,"Commercial-SKT",0x05012715,202103121
+QMBNCFG: "List",18,0,0,"Commercial-KT",0x05012C0D,202108241
+QMBNCFG: "List",19,0,0,"Commercial-LGU",0x05012626,202108241
+QMBNCFG: "List",20,0,0,"Commercial-USCC",0x0504FC40,202011111
+QMBNCFG: "List",21,0,0,"Optus-Commercial_VoLTE",0x05800CA2,201910241
+QMBNCFG: "List",22,0,0,"STC_Saudi_VoLTE",0x0501FE01,201912231
+QMBNCFG: "List",23,0,0,"Commercial-Rogers",0x05018821,202108021

OK
AT+QCFG="ims",1

OK
AT+CFUN=1,1

OK
AT

OK
AT+QCFG? 

ERROR
AT+QCFG="ims"

+QCFG: "ims",1,0

OK
AT+QMBNCFG="select"

+QMBNCFG: "Select",ROW_Generic_3GPP

OK
AT+QMBNCFG="autosel"

+QMBNCFG: "AutoSel",1

OK
AT+QMBNCFG="select"  

+QMBNCFG: "Select",ROW_Generic_3GPP

OK
AT+CGMM

EG25

OK
AT+GMR

EG25GGBR07A08M2G

OK
2

Dear Customer,

Thank you for providing the detailed AT command logs and test results. Based on the information you shared, the EG25‑G module and firmware EG25GGBR07A08M2G are operating as expected, and there is no indication of a hardware or firmware malfunction.

From the outputs, IMS is already enabled on the module (AT+QCFG=“ims” shows IMS=1), and the IMS APN is correctly defined in the PDP context list. The MBN list is also present, and the currently selected profile is ROW_Generic_3GPP, which is the correct default profile for general use when a carrier‑specific VoLTE profile is not explicitly required or supported. Enabling IMS again and performing a CFUN reset does not change the behavior, which indicates that the basic IMS configuration on the module side is already complete.

However, it is important to note that VoLTE and IMS registration cannot be achieved solely by configuring the modem. Successful IMS registration depends on explicit SIM and network provisioning by the mobile operator. Even when IMS is enabled on the EG25‑G and an IMS APN is configured, the network will reject IMS attachment if the SIM subscription does not include VoLTE/IMS services. In such cases, the modem will remain IMS‑idle despite correct local configuration. This is a normal and expected behavior.

Regarding the MBN profiles, although multiple VoLTE‑related profiles are present in the firmware, selecting a different MBN profile will only be effective if it matches the operator’s VoLTE configuration and the SIM is authorized for IMS services. Using an incorrect or unsupported MBN profile will not enable VoLTE and may even prevent network registration. Therefore, unless the operator explicitly recommends a specific MBN profile for your SIM, continuing with ROW_Generic_3GPP is correct.

In summary, your current results indicate that the module side configuration is correct, but IMS registration is being blocked at the SIM or network level. Firmware updates, additional AT commands, or further local configuration changes will not enable VoLTE unless the operator provisions IMS for the SIM you are using. We recommend confirming with your mobile operator whether the SIM subscription supports VoLTE/IMS and, if so, whether a specific MBN profile is required for EG25‑G.