I would repeat Debra's question as to whether the error is in the verbiage of the medical note or only in the CPT code used. You have a HIPAA right to get either one of these corrected, but you should first know what it is you are requesting! (Regarding your difficulty in getting records from them, they have a HIPAA obligation to provide the records within 30 days of your written request. (They can have a 30 day extension if they notify you within the first 30 days that they will need it, but they only get one extension.)
To expand on Annette's answer, if the problem is with the actual record (not just the ICD-9 code), and you make a written request for an amendment of your medical record, they have 60 days (plus one 30 day extension if they have notified you in writing within the first 60 that they will need it) to either make the change (and send - at no charge - a copy of it to you and anyone else they had sent the original record to) or to send you a letter stating that the record is already accurate. (You have no obligation to prove to them whether or not the record is accurate; it is up to the provider to either stand by his record or admit that it was faulty. And the provider's obligation to comply with this HIPAA requirement is not dependent on your agreement to get additional tests!)
If the provider replies that the original record was accurate, he is not required to amend it. However: (a) You have the right to write a statement of disagreement, which he must include (along with your original request for amendment and his reply/replies) or an accurate summary of those, in any future releases of that medical or billing information. (b) If he insists that it is correct when you know that it is not - or if he fails to respond in the prescribed time-frame to your request for records or for the amendment - then you have the right to file a written complaint to the Office of Civil Rights for a violation of your HIPAA rights.
If the problem was only with the CPT code, although HIPAA would theoretically protect your right to get an amendment there, too, it may be simpler to go directly to your insurer and see if they will be willing to do the work for you. Once you have advised them that they submitted an incorrect code, I would hope that they would want to request records and/or take back the payment until the claim is corrected.
diagnosis codes, diagnosis coding