Costco customers complain about card switch to Visa from American Express

Costco's transition from American Express to Visa is drawing complaints from customers.

On Monday, Costco ended its 17-year exclusive partnership with American Express.

Social media is filled with customer complaints.

Many say their new Costco-branded Citigroup Visas have not arrived. Others report problems activating or using their cards or accessing their accounts.

Costco has not commented.

Citigroup says it's received 1.5 million complaints.