Castle Dental Will not refund overpayment from insurance company Missouri City Texas

I received a letter in September 2017 that the insurance company overpaid $495.00 and I was due a refund.  I called and was told I would receive the check in 14 days.  I have called several times and spoke to several people about my refund.  The agent said they had to check to see if I owed another office before sending the check.  I waited two weeks, but did not hear back from anyone.  I called again and the agent said the other office had not responded, so she was going to send the information to the billing department and I should receive the refund in two weeks. 

I waited two weeks and called again.  The agent said my account showed 'paid out' and I should receive the refund any day.  It is December 19, 2017 and I still have not received my money.  I have been calling every two weeks for almost 3 months. 

The reason I left Castle Dental is because while the dentist was filling one tooth on the top, she dropped the instrument and broke my tooth on the bottom.  Castle Dental tried to get me to sign for my insurance to be billed.  I refused because they broke my tooth and I was not going to allow them to bill my insurance company.  The dentist patched up my tooth and I went to another dentist where I needed a crown.