USBI Lied to my child and took the approval from my child San Antonio Texas

 You don't say how old your "child" was, but if your child is a minor(under 18) they can NOT enter into any legal contracts or make any decisions. 

If this is the case you have a very simple situation.  First call AT&T and have your long distance switched back to them.  While you are doing that explain it to them and see if they will remove the amount.  If not then look on your bill for how to dispute your bill...that will usually involve contacting the Public Utility Commision(or what ever is the equivalent where you live).  You will most likely need to send in the disputed amount with your dispute, but they won't cash the check unless it is decided against you..if it is decided in your favor you get the check back.(but again it may be a bit different where you live so be sure to read what the process is).

Now, if what you are saying is true then when you file a dispute with them you can almost guarantee that the charges will be removed within a day or two(phone companies HATE having the PUC involved and will do almost anything to avoid issues with them). 

Now, if your child is 18 or older, then you may not have as much success but it would still be worth a try.