As best I can understand, which isn't saying much, I agree you should try contacting Delta again. Suggest you be clear you were inquiring about "Medallion Complimentary Upgrade" benefit as a Silver Medallion member when the situation went south. Provide tix code details, etc.
Less wording about your deaf situation and opinion of what the GA is/was possibly thinking might help streamline the basic (lack of upgrade request) message/inquiry as well?
Good luck!