Incorrect billing

I resolved issues with regards to my billing with one department only to be told later that the same problem reported previously is still occurring and has not been resolved. I don't understand how one department can assist you only to be told that the information was not communicated to them or logged on their system. This is highly frustrating and should be resolved before more customers suffer the same fate of incorrect billing for times that have been returned to stores as per contract terms stipulated in the NCA.