She had gone into the salon for a $5 haircut.
But over a period of seven months, Madam Betty Chia, 62, ended up paying $5,000 for hair treatments to the New Station Beauty and Hair Salon in Ang Mo Kio.
And it would have been more if she had not exceeded the limit on her credit card.
Her son, Mr Jason Ong, later went to the company to ask for a refund on her behalf.
The businessman has also filed a complaint with the Consumers Association of Singapore (Case).
He is one of 22 people who have complained against New Station to Case in the past nine months.
In Madam Chia's case, it started when she was at Ang Mo Kio town centre in March. She went in for a $5 haircut at the salon.
After cutting her hair, a salon employee offered to do a free scalp analysis.
When the analysis was done, she said Madam Chia had problems with her scalp.
Madam Chia told The New Paper: "They showed me images of my scalp and told me that I might lose my hair. I was scared."
The salon staff said she could have a one-time treatment for $298, but they tried to persuade her to sign up for a 20-session package that would cost $198 each time, saving her $100 per session.
Madam Chia, who earns about $2,000 a month as a cashier, said she was deterred by the cost and insisted on paying for just one session.
But she claimed that when she handed over her debit card, the cashier charged her an amount close to $4,000 and insisted that she sign for it.
"I kept asking her why she had done that as I hadn't agreed to the package. But she insisted that she could not void the payment on the card," Madam Chia said.
She also claimed that the staff made her sign up for another $2,000 hair package that promised five free sessions and hair dyeing credits worth $500.
Madam Chia could not recall the exact cost of the packages she signed up for that day.
She said: "On the same day, I insisted that they give me back $1,000 and they did so in cash. I had to give up the free sessions as a result.
"Since I managed to get some money back, I was not so angry after a few days. So I decided not to tell my children about it." Madam Chia said she was asked to sign up for another package worth $4,000 earlier this month as the condition of her hair had not improved after 11 sessions.
But she could only pay $1,300 of the $4,000 as she had maxed out her credit card.
She said: "They told me that I could pay the rest by monthly instalments".
Mr Ong, 38, went to the salon later and managed to get a cash refund for the $1,300.
Madam Chia said: "Thinking back, I'm really angry about the tactics they used to make me sign up for packages.
"They just kept showing me numbers and I got confused after a while."
But she admitted that she could have been more adamant about not signing up for them.
The manager of New Station's Ang Mo Kio outlet, Ms Huang Anqi, said the company has never forced anyone to sign up for a package.
"We will recommend that customers sign (up for) packages that benefit them because it's a lot cheaper.
"Our management has stressed during meetings that we should not force anyone to sign up," she said.
Ms Huang also said the salon refunded $1,300 to Madam Chia out of goodwill.
"Many of our customers are happy after signing up for packages. But after going home and speaking to their children or spouses, they might change their minds."
When contacted, a representative of the company declined to comment further, except to say it had set up a 24-hour hotline to deal with customers' feedback.
According to its website, customers can call 9615-8968 or e-mail email@example.com. Mr Ong is worried that other elderly folk could be facing a similar situation like his mother.
"These salons are located in the heartland.
"They lure them in with cheap haircuts and then try to sell them expensive packages."