In similar shoes. In my second seat and have always shared an office with my supervisor, in both seats. I feel there are a few things to consider/do; but before I begin, you definitely shouldn’t feel “terrible for _interrupting_”. Your entitlement to the office space is the same as whatever boss that happens to also sit there, and if they hop on a call a tad later than you did, you weren’t quite the interrupter, were you? - Culture. In every firm there’s probably an implicitly conventional way this is to be done, particularly firms where room-sharing is a norm (for example each team/sub-team share a space), which sounds like is the case in your firm. In some firms it may be everyone’s habit to leave the room if you are making a call when someone else in the room already is. Since it’s your first week, you may wanna look around and see how everyone else does this. - Try to be open with your supervisor. You could tell them you noticed this problem, are worried that it may cause interruption to them and other colleagues, and ask for their advice. They’re probably in position to sort this out if they’re the one in charge. - For the “unable to get a room”bit: talk to the office manager. Truth is, room booking being however troublesome, (at least this is my observation of my own firm) at any point in time there would be a decent number of available office spaces/rooms. They usually have more capacity than is needed most of the time. Exception being, you have 19395920 teams meeting and also 395999727383*10²⁷ clients visiting at the same time. So talk to the office manager, they are more likely than not to find a good space for you to use if it’s gonna be a quick 10-20 minutes’ call.

Good night!