Prepare SIM cards from each operator
1. Insert one SIM card in slot 1 and another in slot 2
2. Find the SIM toolkit under All Apps and click through each option or function in the SIM toolkit and while launching function under SIM toolkit, make 1 MT call
3. Swap the SIM card in slot 2 with slot 1 and repeat step 2
4. All SIM cards should go through step 1 to 3"