Playing the Part

Over the years I've found several techniques that, no matter how trained the security personnel of a corporation is, tend to work one way or another.
In this case "the angry executive speaking in another language on a cellphone".

I've used this many times and with good results. After researching a bit the target, learning what are the baselines in term of dress code for the top executives and diversity of the employees, coupled with the atmospherics of the location and its patterns of life, you can put together a very credible employee from another office act.
The idea is both show that you belong there, but that you are coming especially coming here from another location. It causes whoever happen to be in front of you to be a little more sympathetic.

In one particular case, I was outside, on the street, but the booth keeping the entrance to the underground parking. The guard was looking at me. I was wearing the proper suit and tie, with a fake, though very realistic badge clipped to my jacket's pocket. On cue, another guy from the team call my cellphone. I answered in English and switched to another language. I increasingly become more and more agitated as minutes passed. The guard kept an eye on me. I made it a point to walk back and forth the booth, and give him consternated looks. He began giving me small smiles... And after about 20 min, he lost interest in me. Having seen my badge and sensing that I belong there.
Once I saw that, and still arguing on the phone, I slowly began walking towards the parking. Going down the ramp step by step, still on the phone still gesticulating and never looking back, at the guard. I belong there, right? I wouldn't worry about the guard.

Boom. I was in. I was freely walking on the underground parking.

Next was to get inside the building. My badge was a good copy, but it wouldn't open the door from the underground parking to the elevators. So I stood there, still angry on the phone, until 5 min later, someone came back to his car. As he walked by me, i gave him a smile as I walked in. He never questioned me. So... Now I was really in.

After that it was just stuff, but, once you understand the environment, and know how to play the part... It's just a matter of time.