Nai nai S and S-jee. It’s a matter of where you draw your boundaries. You’ve just said phone calls are stepping over the line for you - whereas others have argued that a casual phone call is okay. So, are YOU insecure about your relationship?
I draw the line at out-of-necessity interactions; be it lunches, phone calls, socialising after work. All that jazz. I don’t deem it necessary to engage with one-on-one social interactions with members of the opposite sex unless you don’t have a choice. If the guy can choose who he has lunch with - don’t choose a girl. Simple.