Verizon lets you access your phone and texts through its mobile app, but I think it blocks short codes. US Mobile will give you a real mobile number for $6 a month where WiFi calling is enabled. If you have a dual SIM phone, you could use it over WiFi. If you have a dual SIM phone which supports WiFi calling, another option is to manual lock your Verizon phone on your Verizon signal in the US before boarding the plane and connect via data assist over your French SIM. Incidentally Orange FR just released a data only roaming SIM.