Is it illegal to bring a video carmera to the post office?

So I'm goin on battle with my local post office. Who by far is the WORST post office I have to deal with. On the weekdays I typical pack my items and travel 30 to 45 minutes to ship my items. My local post office is 5-8 minutes away. As a last resort (mostly on the weekend) I ship from there. Although, my packages are labeled I do request them to be scanned because it has happened numerous times were my package get lost or the tracking number never shows any activity. For example I shipped an item going to UK 2 months ago from my local post office, and to this day the activity stills says its still at the local post carrier. I even request a pick up, and when they do pick up they either pick up 5 days after or I get an email of "theirs was a discrepancy on the amount of items that you requested to pick up" BS! So now my last resort is to bring iPhone and record what's actually happening. So the district manager is telling me its illegal to do that. Illegal my ***, if your people were doing their jobs I would have to. So is it really illegal to record them.

No, you can't take a video into a business or federal building unless you have approval first.