There used to be (maybe still is) an 800 number you could call to get your ANI, basically the billing number for whatever phone you were calling from. Kinda fun.
The old mci number, died last year finally unless there's another still up
There's a few:
800-437-7950
800-223-1104 (passcode 910777)
For the second one, I'm getting "Please, enter your password", then, after typing the passcode – "The toll-free number you have dialed has been disconnected. No further information is available about this number. 074T"
Whatever method you're using to send touchtones is likely not working then. You might want to try using something else to send it.