Hi, mine is unlocked. The second sim is opened for other networks for my S9+ no problem whatsoever
I concur - you can use other network's SIM card in either SIM actually. I have a Globe-issued S9.
However, i did notice that I cannot get 4G/LTE with my non-Globe SIM. In the phone settings to change network mode the option for LTE is grayed out for the foreign SIM; switching between SIM1 and SIM2 didn't help either.
I know the foreign SIM is capable of LTE, because it works in another phone. Does anyone have this experience? Is this the new way of 'locking' a phone to a specific carrier?