I had the same info given to me yesterday when I called that number listed on IRS to cancel. I was told that I needed to go back to Turbo Tax who I scheduled it through or call the main IRS number and get help on individual taxes, that it was only for EFTPS (Electronic Federal Payment Tax System). So I tried the main number which has a recording they are too busy and you can not get through today. Turbo Tax has also nothing on it's website of who to call to cancel your payment, only that the are waiting on the IRS on how to move back your payment date with the new March 2021 filing extension.
I decided to call the number I saw on the IRS website again this morning, and the woman canceled my payment asap and gave me a confirmation number!!! I asked her why I was told I could not do it when I talked to someone yesterday, she immediately said that person is probably new and not reading their most current info. So call back that number and keep trying until you get someone experienced that knows their job!
