Costco recently ended its long monogamous relationship with credit card partner American Express, leaving to only accept Visa cards and partner with Citibank for a store-branded card. AmEx could lose up to 10% of its customers over the switch, since the number of people who had cards with them just for Costco is huge. The switch went badly for some Costco customers who didn’t get their cards, couldn’t activate them, or had other problems with the switch. Citi’s CEO promises that he’s going to fix this.

While many functions for the new Costco Visa cards could be taken care of on Citi’s website, that didn’t work for everyone early on, and wasn’t helpful for customers who were concerned that their cards hadn’t showed up at all.

“[W]e’re working through that, Citigroup CEO Mike Corbat told analysts during a conference call on Friday. “We’re gaining on it. We’re very focused on it.”

The company deployed additional customer service agents after customers’ call times were as high as thirty or forty minutes shortly after the change.

Customers seem to be embracing the Visa cards, though, spending $5.7 billion already even though at the time they had the cards just short of a month.

Meanwhile, AmEx is traipsing around with a much younger, online-only bulk retailer, Boxed.

Citi CEO Says He’s Focused on Fixing Costco Credit-Card Woes [Bloomberg]

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