Does RC76xx need reset after APN setting

I have RC7611 with R10 firmware. I am trying to understand what is the correct way to set APN. From AT command manual, it is at+cgdcont to be used for setting APN. But many networks seems to auto-fill this. The question is, when to know if the user needs to set APN and when to leave it empty? Also, in case of Verizon, the PDN context seems to be # 3

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”,“VZWADMIN”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0
+CGDCONT: 3,“IPV4V6”,“VZWINTERNET”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0
+CGDCONT: 4,“IPV4V6”,“VZWAPP”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0
+CGDCONT: 5,“IPV4V6”,“VZWEMERGENCY”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,1
+CGDCONT: 6,“IPV4V6”,“VZWCLASS6”,“0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0”,0,0,0,0

How to know which number to set APN, if the user is allowed to use any SIM card of his choice, with RC7611?

Regards,
Sai.

you might need to ask the network operator which profile and APN to be used

And how to enable/disable roaming in RC76xx?

You can see here