Transporte Terrestre counters at the airport

When I arrived at the airport last year, I didn’t need to go through customs/immigration since I traveled through Mexico City (where all that was accomplished). I just grabbed my luggage and walked out the door. In over 25 years of traveling to the area, I have always traveled through US airports so this was a 1st. There was a shelter outside where I was able to purchase my cab with a credit card. In previous years, going through customs, you walk out of the airport to a different area and I’ve never seen a way to pay for a Transporte Terrestre taxi with a credit card. Have I been missing it all these years? I will be going through customs this year and would prefer to pay with a credit card. Where (exactly) do I do that??