I was sent a bill from my max benefits but I already paid it

This is the public user forum.  No one here can access your account or authorize any sort of refund or adjustment for you.  You can make your request with Customer Support.  Use the word ”billing” instead of the word “refund.” 

To call TurboTax customer support

https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number

They are available from 5 a.m. to 5 p.m. Pacific time Monday - Friday.

Are you talking about MAX benefits for your 2018 return?
Did you use Free Edition but added the optional MAX product at the time of filing?   If so, how did you pay for it?   Did you pay by credit/debit card upfront at the time of filing, or did you choose to pay the fee out of your Federal refund?

If you chose to pay it out of the Federal refund, has your refund been delayed at the IRS, so TurboTax sent you a bill?