On different receipts issued by TSC, I saw that number to be 214-381-1423.
One needs to try continuously to get through that number. One time, I dialed continuously for about two hours, did not get through. The next day, I dialed for about one hour continuously to get through, I was on hold for about an hour to get a chance to talk to an IIO. I needed to change my address, so I was desperate.