The concession vendor for the popular Major League Soccer club FC Dallas says it is giving refunds to customers after a glitch in a credit card machine recently billed some people for charges from as long as two years ago.

The vendor, Legends, said Thursday it was still investigating how many people were affected and whether they were charged twice – or simply very late.

“We’re on it,” said Eric Gelfand, Legends’ senior vice president of communications and brand strategy.

Gelfand said the company recently upgraded its credit card machines and old charges somehow reappeared.

Word of the mystery charges surfaced on Twitter.

One man wrote, “Saw charges B4 Valentine's & thought my wife had purchased FCD stuff 4 me but she did not."

Some fans said they noticed credit card charges from FC Dallas even though they hadn’t been to a game at Toyota Stadium in Frisco in two years.

The club started getting calls several days ago.

"We immediately began looking into it and discovered that it stemmed from a system upgrade we did on our concession terminals and immediately began trying to rectify the situation,” said FC Dallas spokeswoman Leigh Anne Gullett. “We're in the process of refunding those charges."

Gullett stressed that no credit card information was compromised and that refunds should be finalized in the next two weeks.

"We're still investigating and trying determine what caused it and what the scope is,” she said. “We’re going to make sure that they get their money back."