BG96 can't connect NB-IOT

IoT Modules
1

Hi there, I am trying to connect to NB-IOT network but I get error when calling AT command: AT+QIACT=1. ERROR. But when I calling AT command: AT+COPS?, I realized I was connected to the GSM network. Anyone have a solution for this problem?
Below are my full AT commands:

at+set_config=cellular:(AT+COPS=?)
AT+COPS=?
+COPS: (2,“Viettel”,“Viettel”,“45204”,0),(1,“VN VINAPHONE”,“GPC”,“45202”,0),(1,“VN Vietnamobile”,“VNMOBILE”,“45205”,0),(1,“VN Mobifone”,“Mobifone”,“45201”,0),(0,1,2,3,4),(0,1,2)
OK

at+set_config=cellular:(AT+COPS=0,0,“VIETTEL”,9)
AT+COPS=0,0,“VIETTEL”,9
OK

at+set_config=cellular:(AT+QICSGP=1,1,“v-internet”,"","",1)
AT+QICSGP=1,1,“v-internet”,"","",1
OK

at+set_config=cellular:(AT+QIACT=1)
AT+QIACT=1
ERROR
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at+set_config=cellular:(AT+COPS?)
AT+COPS?
+COPS: 0,0,“Viettel Viettel”,0
OK

2

based on your description ：
AT+COPS?
+COPS: 0,0,“Viettel Viettel”, 0

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it means that you have register on GSM successfully

pls send AT+QIACT? to query the PDP context .

if the PDP exist already , pls do not active it again with “AT+QIACT=1”

3

Thank you for your help. I finally solved my problem. The problem is in my Sim card. I changed another sim card and everything worked smoothly!