Turbotax Wrong State Tax Calculations- Terrible Support - Looking for suggestion on next step in escalating this issue

I contacted Turbotax to report a wrong calculation of one aspect of state taxes. I have verified that Turbotax is wrong with the state tax authority so I am 100% sure about it. I have a specific communication from the state tax authority confirming it. Turbotax support (even the Live Tax Advice - Stephanie) was terrible and did not care to follow up or really verify the information. I offered to share the reference information from the state tax authority site but they did not want it; they could not care less.  I asked to speak with a manger and they simply hung up on me. I have been using Turbotax for so many years and I was a happy customer. I am so disappointed now. The 100% accuracy guarantee is not reliable.  Unfortunately, the calculation error results in taxpayers paying more taxes than they should. I realized that recognizing this  would be a major problem for Turbotax as they would have to tell their clients that they messed up. So, the likelihood of me addressing this is extremely low.

Has anyone else encountered a similar situation? What is the next step in terms of escalation?