Half payment despite authorisation

We had fitting of hearing aids approved in March 2022. this was an amount for 2 hearing aids. Authorisation was provided. Payment for only one hearing aid was made in September. when we queried this, it was stated that the authorisation was incorrectly captured for a quantity of 1. We then received an authorisation for a quantity of 2. A resubmission of the claim was made on October 2022. We have been calling and trying to get payment for the other hearing aid since October and no one has been able to assist. Consultants are rude and do not listen to the provider. 10 months to get payment is totally ridiculous!