Amex Credit Card Complaint

Amex Credit card department,

Transaction issue North Carolina

Hello I am using Amex credit card, i purchased apple watch from - local store on -/-/2016 for $370.00 for my wife and she just changes her mine and we return that apple watch at same place in ( - ) store on -/-/2016, When i checked online in my credit card account i see instead of credit of ( $370.00 ) on -/-/2016 they charged me again so they charge me again. I called Credit card company twice and they just give me credit of ( $370.00 ) and still they need to give me credit of remaining $370.00 since they charged twice. Also - charged me $370.00 in my - account as well and when i called even - representative not responding properly. Can you help us here please. Let me know what legal documentation you need any statements or item return bill from - company. Thank You - -