Each SSN is a new client, and a new fee. 

If we could just keep changing the SSN, people would only pay for 1 client return and file dozens or even hundreds of returns.

You may be able to talk support into giving you a free credit for your mistake if you call.

I see - and there is no way to bypass having the client re-sign the efile form?

I have no clue how Esigs work, sorry. If youve got a signed 8879 from the client and just the SSN is off by a digit, I may be tempted to just file it as is and make a note on the 8879 in the file.