By Karen Anderson, WBZ-TV

BOSTON (CBS) – Walgreens is one of the nation’s largest retailers, and they’ve got a big problem on their hands. Across the country, they’re being accused of overcharging customers.

Their weekly flyer features all kinds of great deals. Use a Walgreens reward card, and you will save even more. Missouri Attorney General Chris Koster found Walgreens often failed to deliver on those promises.

“Our findings were disturbing. Investigators from the Attorney General’s office documented overcharges and deceptive prices at nearly every store they visited,” said Koster.

The I-Team went shopping in the Boston area, and it wasn’t long before we found some of the same issues here.

A big problem has been clearance items which are marked down on the display, but full prices are still being charged. It happened to us when we bought a package of pens advertised on sale for $1.29. At the register, we were charged the original full price of $2.49.

There was also a pod of flower seeds which were reduced to 89 cents. We were charged $1.79.

And it happened when we bought a children’s ball as well. It should have cost $3.19, but the register rang it up as $4.99.

Customers say it is frustrating to realize a mistake when you get home and look at your receipt. One shopper said, “Do I want the hassle of having to go back in and take the time?”

Another complaint involves outdated sales tags which consumer advocates say is misleading for shoppers. For example, we found a display advertising Aleve for $5.99. If you looked closely at the tag, you would see the deal has expired. We were charged a full price of $7.99 for the pain reliever.

Attorney General Koster also found that reward cards were not calculating reduced prices for consumers.

We bought two containers of ready to eat noodles which should have earned us 200 reward points. Our receipt showed we only had a balance of 40 from previous purchases.

When told what we found, one shopper said “It’s wrong. Absolutely.”

In a statement, a Walgreens spokesperson said, “We have a 112 year history of acting in our customer’s best interests and earning their trust. That will continue to be our focus in all areas. We always seek to continuously improve, and we welcome feedback on areas where we are not meeting customer expectations. If a customer believes they were charged incorrectly, we are happy to resolve it.”

Attorney General Koster wants to find out if Walgreen’s track record is more than just sloppiness. “This level of consumer deception is inexcusable from a corporation as sophisticated as Walgreen’s.”

The I-Team learned the Massachusetts Attorney General has received 11 complaints over the last 2.5 years from angry Walgreens customers who say they were overcharged.