Thank you both. I did call TurboTax again today. I was told that there is no billing department to take my call but the agent who took the call eventually solved the problem by using a download version instead of the web version of TurboTax. The download version still gave me errors after I submitted my payment, but luckily this version allows the agent to process the payment at their end.
I hope TurboxTax will check and fix my account issues so that they won't make the payment process so unnecessarily laborious if I still use TurboxTax next year.
