Could be just the sales staff who attended to you who have made a mistake. With all the young or foreign chaps, these mistakes seems common nowadays. Just go down to the branch to clear it up. The customer service on the phone do not have the full picture and can only refer to the records in the system. If they don't value you, they would not have waive off $200. So no need to make a big fuss and bring in a third party to complicate things further. Just make the trip down to the branch to resolve the dispute.
If you refuse to make the trip because you are in the right. Then we all know where the problem of this dispute lies...