Citibank Credit Card Complaint

Citibank Credit card department,

Transaction issue Utah

I used - - Costco credit card until they issued new credit card from Citibank as the exclusive Costco credit card. Beginning balance with Citi was $330.00 higher than the ending Costco balance. I 've tried to get Citi to acknowledge the error and they just keep sending me copies of their statements and not addressing the problem.