SIM7600 AT conference calling not working

I

'm using a SIM7600A-H and I can make a voice call, add another call, switch between calls by placing one on hold but I cannot merge the lines.

atd<number>;
OK
atd<number>;
OK

AT+CLCC;
+CLCC: 5,0,1,0,0,"<number>",129
+CLCC: 3,0,1,0,0,"<number>",129

AT+CHLD=3;
+CME ERROR: network rejected request

I've verified that the SIM can do conference calling by putting it in a cell phone for testing and it works fine. Is there an additional command that allows conference calling? I can also switch between calls by using AT+CHLD=2;

At command + manual can be found here: https://www.waveshare.net/w/upload/6/68/SIM7500_SIM7600_Series_AT_Command_Manual_V2.00.pdf

I used sim800 instead of sim7600 in the tags because my rep isnt high enough to put the correct model, but the commands are mostly the same.

Thank you.