It is a common story among teens: Order an SMS ringtone and next thing you know your mobile phone credit is gone or a bill arrives in the mail for an exorbitant amount.

Carly Portch was one such “victim”.

“I got myself in trouble when I bought a ringtone when I was in year 10,” she said.

Carly thought she it would cost $4.

“But then I started getting all these messages and they were charging me $1.20 every time,” she said.

“I ended up having all my credit eaten.”

When she contacted her phone company, Carly was told the biller was a different company and they couldn’t help.

Sian Malouf had a similar experience after signing up for a ringtone. She later attempted to make a call and her $25 credit had disappeared.

The 14-year-old said she called constantly to try and cancel the service and just kept being cut off.

“I just ended up getting a new SIM card and new number,” Sian said.

Shahni Willis said she had never been caught out, but had a friend who had been “seriously burnt”.

“They signed up to something and the next thing he got was a bill for more than $200,” Shahni said.

The Telecommunication Industry Ombudsman’s Phillip Money said they hoped the new rules, which came into effect on Wednesday , “would protect the thousands”.