Dismal service

Ordered form Amazon this morning using my new Discovery bank credit card. Hours later, got a SMS- card declined. Tried later in the day ( now costing me more because exchange rate changed), again declined. Phoned bank: ***. Was told that card was declined because of " suspicious activity", Discovery should have a recording of the call. No one contacted me to verify this. Checked Amazon- now I had ordered two belts. Tried to cancel one- got a message: may be too late to cancel- may have already shipped. Had an FNB card for 25 years - never had problems like this.