An O2 customer has been outraged to discover that, following a complaint, the word 'idiot' was added to her account details.
Aaisha Hussain, from Oldham, called the company last month to ask about upgrading her contract and recycling her old phone. But the operator couldn't help, and her call was cut off.
When she then received a message asking for her feedback, she complained.
But after she called the company back about another issue, she was stunned to discover that she failed the security questions - because her mother's maiden name had been changed to 'idiot'.
Disgruntled Amazon customer gets more than he bargained for
"I started crying. This is my mum's maiden name, it's a personal issue," she tells the Manchester Evening News.
"I'm a very family-orientated person. It's so childish of them to do this, it's embarrassing. I'm utterly disgusted with what has happened and how I've been treated. I want people to know what they have done."
EE emails customer calling him a f*****g c**t
We annoy customer service staff at our peril - and they often take revenge. Sometimes, it's very direct, such as the time an EE call handler emailed a customer calling him a 'f*****g c**t' after the pair had argued on the phone.
Often, though, they hit back in the same sort of sneaky way as the O2 worker. This time last year, for example, an Amazon customer who had previously complained about customer service got a surprise when he logged into his account - a ten-inch sex toy had been added to his shopping basket.
And insulting names are often added to restaurant receipts - and discovered by the victim. A Pizza Hut customer was described as a 'pink fat lady' in 2014, for example, and three women as 'fat girls'.
In this latest case, O2 has apologised and offered Aaisha £75 and the chance to upgrade her handset early. But she says she has still contacted the ombudsman to try and make sure that the same thing never happens again.