I filed my federal taxes (2020) and sent a payment with the payment voucher turbo tax gave me, and IRS did not give me credit towards my balance. My contact number is [phone number removed]
Which voucher did you use when you sent the payment? Did you use the one that said 1040V ?
If you used one that said 1040ES that would have been for paying estimated tax for 2021. Have you seen money taken out of your checking account or credit card account? That is your only proof that you paid tax due.
Check your account on the IRS site: