Call. Can't you get a 5 min window out of your normal day to day activities?
Instead of going to the restroom go outside and call?
Any excuse to go to your car and make the call?
Book a conference room, and call with your cellphone?
Either at your normal lunch time, or get to lunch earlier than normal and call before their lunch time. Or get a late lunch, and call after their lunch time.
"Skip" lunch and go there.
Can't your current boss help you in any way?
Time to be creative and get some direct contact with them, or face to face time with them.
Can you justify a visit there?
You mentioned that you already are working inside the company, can you get to the areas where you would like to work?
Find a way to know people in that area, and mingle.
Don't allow the fear of getting a rejection to be bigger than your wish to know what happened, or actually getting the job.
Keep in mind that if this is not the right time, there will be a better one.
In my current job, I was interviewed for a global position first, they didn't hire me, as they preferred a "more experienced" person.
6 months after that I was called for a less senior position, and I took it.
The person that was hired before me was earning way more money than me, but when they needed to restructure they let him go. He was way more expensive and not using all the skills that his resume "said".
My point is that most of the times whatever happens is better.
And sometimes is better to be the second choice, as the first choice is not always the best for the hiring manager, nor for the person that is hired.
Be careful what you wish for, as it may become a reality.