I have included a helpful FAQ regarding when your tax payment will go through:
https://ttlc.intuit.com/replies/3299924
If your return was e-filed and 'transmitted', you are unable to make any changes until it has reached an 'accepted' or 'rejected' status. Please find some additional information in the following FAQ regarding this matter.
https://ttlc.intuit.com/replies/3301669
If you haven't filed yet (or e-filed but was rejected), you can proceed through the File section again to choose a different payment method.
Finally, here is some additional information on paying your tax bill in TurboTax:
If you already filed your return with the IRS, visit www.irs.gov/Payments and choose a payment option instead of trying to pay through TurboTax.