Use the link already provided to you if you need to talk with customer support.
If you mean that you made a mistake of some sort on your tax return and it was filed with an incorrect amount, you cannot do anything about it now. If the return was accepted you have to wait until the IRS processes it fully and then you can file an amended return. You cannot stop an e-file or fix a mistake right after e-filing.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
