Cigna sent me a letter changing a billing code for an ER visit – will I get another bill?

I got a letter in the mail from my insurance saying that they have finished reviewing a claim for an ER visit that happened back in July. They said that based on the available clinical information, they determined that not all “Current Procedural Terminology codes accurately reflect the level of service provided”.

The difference in the described codes seems to be that the hospital charged a code describing “Medical decision making of high complexity”, while the insurance reimbursed code describes “Medical decision making of moderate complexity”.

The letter says that I can appeal the process, but I already made a payment back in July or August for this visit and I have already reached my insurance deductible. Will I get another bill for this same claim that I have already paid? Should I appeal it, or just wait and see what happens? The total claim charge is close to $3,500, and I had to pay several hundred for the initial visit bill I received.

Living in North Carolina.

Thanks.