Amex Credit Card Complaint

Amex Credit card department,

Rewards Michigan

I applied for the Platinum Card from American Express with offer spending $3000.00 for the first three month then I can get - membership reward points on - 2016. And I did spend a total $3600.00 ( exclude $450.00 annual fee ) within first three month. However, I do not know why my - points were claimed back on -/-/2016. I did not get any kind of notice or explanation. I do contact customer services serval time, and was told that I might return something and made my total spending less than $3000.00, after I checked my billing statement I am sure that my total spending were more than $3000.00. I feel so disappointment about this behavior of American Express.