Please try the following:
Set the sim slot with the vodafone sim to 3G and see what happens?
If that doesn’t give you the option to call, switch it to 2G.
Just for the purpose of detection .
Are you using two SIMs at the same time or only the vodafone SIM? In the former case, please try using only one SIM.
Did you try it in multiple places? Perhaps there is bad reception because of the FP2 with the vodafone SIM at the place where you are?
Does this mean you tried on FPO(O)S first?
Also, as LOS currently has mobile data issues I wouldn’t consider the most reliable OS for testing SIMs…