I electronically filed my return and it was accepted on July 6, 2021. I haven't received my refund. Who can I contact.

Only the IRS can assist you with the status of the 2020 tax refund

Call the IRS: 1-800-829-1040 hours 7 AM - 7 PM local time Monday-Friday
When calling the IRS do NOT choose the first option re: "Refund", or it will send you to an automated phone line.
So after first choosing your language, then do NOT choose Option 1 (refund info). Choose option 2 for "personal income tax" instead.
Then press 1 for "form, tax history, or payment".
Then press 3 "for all other questions."
Then press 2 "for all other questions."
- When it asks you to enter your SSN or EIN to access your account information, don't enter anything.
- After it asks twice, you will get another menu.

Press 2 for personal or individual tax questions.
Then press 4 for all other inquiries
It should then transfer you to an agent.
Or you can contact your local IRS office. See this IRS website for local IRS offices - http://www.irs.gov/uac/Contact-Your-Local-IRS-Office-1 or call 1-844-545-5640 to set up an appointment
Or you may want to contact a Taxpayer Advocate in your area. See this IRS website for Taxpayer Advocate in your area and a toll free number - http://www.irs.gov/Advocate/Local-Taxpayer-Advocate