Sister Donna Williams says she didn’t buy a $1,359 Aeromexico Airlines ticket from a Houston travel agent. The Eden Prairie nun didn’t access her credit report eight times in three months, though her credit card statements indicated she had. She didn’t buy a last-minute $1,080 round-trip ticket on Iberia Airlines from Malaga, Spain to Caracas, Venezuela two months after the Aeromexico purchase.

If someone had told her it would take almost two years to remove the bogus charges from her credit card bill, she wouldn’t have bought that, either.

Williams has been battling her credit card company, Citi, since May 2011 when she first reported the bogus charges. Four billing statements in a row contained disputed charges, and Williams was issued first one, then another new card in an effort to curtail the unauthorized use.

Williams called to report the charges after receiving the bills, and customer service reps assured her the bills would be adjusted, she said. Nonetheless, the charges remained month after month, accumulating interest.

In August 2012, 15 months after Williams first contacted Citi, Citibank Security Services sent her a letter stating she would be responsible for the charges. Because “the merchant supplied your correct account information ... [and] statements reflecting these charges were sent to you,” Citi is “unable to assist in this matter.”

The rest of the letter gave her advice on monitoring her account and notifying the company “within 60 days of the statement in which the disputed charge appears.”

She thought she had done just that when she made the phone calls.

“I am a Roman Catholic nun. I do not have [money] to pay for someone else’s plane tickets, etc.,” Williams wrote in response to Citi’s letter.

On Thursday, Citi agreed to remove the charges and related interest, which today add up to around $5,000.

“We appreciate that Ms. Williams’ concerns were brought to our attention, and based on the new information provided, we have credited her account for the unauthorized charges,” Citi spokeswoman Emily Collins wrote.

What went wrong

In the early months after she immediately reported the fraudulent charges, Williams didn’t think much of it. “I was always assured that they would be investigated,” she said.

Many websites, including those of the Federal Trade Commission and the Better Business Bureau, say that once the phone call is made, a customer is off the hook.

But according to the federal Fair Credit Billing Act, that’s not entirely true. A customer who calls in suspicious charges has no liability for future unauthorized charges, but to be sure that any fraudulent charges already on a bill will be investigated, a credit card company needs to be notified in writing. No e-mail. No fax. Within 60 days from the date the bill was printed and to a certain address reserved for billing inquiries. Not the address where payments are sent.

“While we encourage card members to contact us by phone immediately if they notice suspicious charges, we also ask that they follow up with us in writing so we can investigate,” Collins said.

Williams said she wasn’t told to do so.

She’s not alone, according to the Consumer Financial Protection Bureau. The bureau has received more than 30,600 credit card complaints in almost two years, with “billing disputes” the most common complaint.

“Some consumers realize only after their claim has been denied that they needed to notify their credit card companies within 60 days of any billing errors,” according to a recent bureau publication.

Citi’s densely packed cardholder agreement describes the complaint process. Collins said instructions are also printed on the back of each bill.

‘I am not the crook here’

By August, four disputed charges remained: the plane tickets and two credit-report fees. The rest of the charges, $40 eBay gift cards, a handful of credit-report fees at $14.95 a pop and a few others were taken off her account by Citibank Security Services.

The law requires credit card companies to conclude a fraud investigation within two billing cycles or 90 days of being notified in writing. Though Williams sent no letter in the first couple of months, she made up for that later in spades.

“Towards the end of the year,” Citi asked her to send in her statements, said Williams, who highlighted the fraudulent charges and mailed them in.

In March 2012, Citi again asked for the statements. She began flooding Citi with letters, sometimes mailed to “security services,” the legal department, or the “Presidential Unit.” “I am not the crook here,” she wrote.

Williams documented call after call to customer service employees Rachel, Penny, Debbie, Diana, Dana, Idania, Lynn, Leslie, Bonnie, Cedric, Cherry and Carlos.

Even after Citi decided she was responsible for the charges, her letter and phone campaign continued. Now, finally, it may be coming to an end.

Citi is going to deduct the bogus charges and related fees and interest from her balance, Williams said on Friday. “I’m so relieved I can’t tell you. It’s like Christmas and Easter and Fourth of July all put together.”