I have paid my 2019 taxes with turbotax and paid for services, I am now getting a letter saying i owe more and interest is adding up

Is for the full amount you paid?  When did you pay it?  If it was after July 15 it might be for interest.  Or if you owed too much it might be a penalty for not paying in enough during the year.

How did you pay it?  Did you send in a check?  Did you use the 1040V voucher?  If you used a 1040ES slip that was to make an estimated prepayment for NEXT year 2020 return.

Your only proof of payment is your bank or credit card statement showing it coming out.  Turbo Tax does not pay it.  They only send your bank info to the IRS or state and then the state pulls it out of your account. 

Or the IRS changed something on your return or added some income.  The letter should say what they changed.

I recently received a notice stating that I owed a penalty and interest for unpaid 2019 taxes.  I suspect that I am not the only one and this is what I think of a the Law of Unintended Consequences.  Typically, a guesstimate my taxes and file by April 15.  For 2019, I finished and sent a check for the entire amount due before the July 15, 2020 extended deadline.  Bear in mind that if I had filed for extension on April 15, 2020 and paid by check that I would have had till October 15, 2020 for the IRS to have processed my payment.  But because the filing date was extended to July 15, 2020 the payment by check was NOT considered a payment made by July 15, 2020 so a penalty and interest was added.  So if you get a similar notice it could be because you did not pay all of the taxes due by July 15, 2020.  Moral of the story, pay online.