It’s only been a few days since Chicago’s tax on sodas and other sweet drinks went into effect, and already some Illinois residents are claiming they’ve been charged improperly for drinks that don’t contain any sweeteners.

Cook County, which includes the city of Chicago, has a new $.01/ounce tax on all sweetened, nonalcoholic beverages. The tax, which went into effect on Aug. 1, applies to drinks with sugar and those no- and low-calorie drinks sweetened with things like aspartame, sucralose, or stevia.

But according to DNAInfo, Walgreens was charging that tax on LaCroix seltzer products, which don’t use any sweeteners, natural or artificial.

Walgreens admitted the mistake at the time, saying the company had “inadvertently coded” some products incorrectly while preparing to collect the new tax.

“We are working to resolve this complex issue as soon as possible,” the company said at the time.

Suing mad

But that “our bad” from Walgreens didn’t fix the coding error fast enough for some customers, like one man from Schaumburg, IL, who says the problem persisted even after Walgreens admitted the error, and that it applied to a lot more than just LaCroix, reports the Chicago Tribune.

In his lawsuit, the man says he purchased Dasani Tropical Pineapple Sparkling Water from a Walgreens store on Aug. 4 — after the company had acknowledged the mistake — and was charged the sweetened beverage tax.

He also claims that another Walgreens store in the area charged the tax on a case of Dasani Black Cherry Sparkling Water that was labeled as unsweetened, as well as on Lipton Pure Leaf Unsweetened Green Tea.

“Walgreens has publicly admitted it is wrongly charging the pop tax on unsweetened beverages — and yet it continues to do so without informing customers that they are being wrongly charged,” reads the complaint. “Despite knowing that it has improperly coded its products, Walgreens has not taken any steps to provide corrections at the cash register.”

The plaintiff points out that even Cook County Board President Toni Preckwinkle — the architect of the soda tax — recently Tweeted that unsweetened beverages are not subject to the soda tax.

He’s seeking a jury trial and class-action status.

Walgreens declined to comment on the lawsuit to the Tribune. We’ve also reached out to the company, and will update this post if we receive any new information.

What to do if you’re improperly charged

Last week, a Cook County spokesman said that although it hadn’t yet received complaints from customers about the tax being applied incorrectly, shoppers should check their receipts after purchasing drinks and ask the store for a refund if they’ve been improperly charged.

“Our ultimate goal is to ensure the tax is being applied correctly and fairly,” a county spokesperson told DNAInfo at the time. “We will continue an open dialogue, as we have for the last eight months, with retailers and work to ensure beverages are being correctly taxed.”

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.