No coverage inside building

So, I am being relocated to an Internal space in my building. I will not have any windows at all and it is a metal building. I was in there the other day to lay out the space, and my phone service was gone completely. I can connect to my company WiFi, but I would prefer not to. I do not have the option to add an antenna of any kind outside the building or any other equipment. I'm afraid my only hope is to see who has other carriers here, and ask them to bring their phone so I can see if they have better coverage and switch my service to one of those. I love T-Mobile and hate to have to switch, but I need cell service at work (and on my T-Mobile iPad), but don't know if I have any other options.

Has anyone else run into this? And if so, is there any solution?