Ever got an unsolicited text message asking you to "Reply YES now" to enter a competition or sign up to a daily horoscope service?

Or perhaps you've been offered celebrity news or a daily quiz via SMS?

Chances are you've been targeted by a premium text messaging service of the kind allegedly operated by Perth tycoon Zhenya Tsvetnenko in the United States.

Mr Tsvetnenko is facing extradition from Australia on a range of charges, with US prosecutors claiming he engaged in "a multi-million-dollar scheme to defraud mobile phone customers by placing unauthorised charges for premium text messaging services" on their bills.

According to the US Department of Justice, it involved mobile aggregators, which compile charges for premium text message services on people's mobile phone bills, and content providers, which sent customers unwanted text messages that led to them being billed.

Zhenya Tsvetnenko is alleged to have been involved in a fraudulent scheme to fleece phone users for unsolicited SMS services. ( Facebook: Zhenya Tsvetnenko )

The services provided included monthly horoscopes, celebrity gossip and trivia facts.

While it is not suggested Mr Tsvetnenko is involved, auto-subscribing or third-party billing schemes operate in Australia as well.

So how do I know I've been auto-subscribed to an SMS service?

You'll usually receive a text message like this one.

Sometimes it's hard to know what service is being offered. ( Supplied: Australian Communications Consumer Action Network )

Often the message will thank you for subscribing to a service you've never heard of and never signed up for.

These "premium" services naturally come with a premium price tag.

Sometimes it's unclear exactly what they're claiming to offer at all, or how to access the content (assuming you want to in the first place).

You may have inadvertently subscribed after you clicked on an advertisement on a website or app.

Or you could have been targeted randomly by companies employing number-generating services.

What sort of services do they offer?

According to Australian Communications Consumer Action Network (ACCAN), there are three types of third party charges that consumers could find on their bill:

Direct carrier billing: this is a service that allows you to charge the cost of content to your phone bill, and is available to Telstra and Optus customers only.

this is a service that allows you to charge the cost of content to your phone bill, and is available to Telstra and Optus customers only. Mobile Premium Services (MPS): these are content services that consumers may subscribe to by calling or texting a 19X number or by subscribing on a website, and the content arrives by SMS or call.

these are content services that consumers may subscribe to by calling or texting a 19X number or by subscribing on a website, and the content arrives by SMS or call. 190 voice or video call services: these are charged by the minute, or at a fixed rate.

While it's not illegal for businesses to provide premium mobile services, they are not allowed to send unsolicited texts.

You may be able to get a refund if you were subscribed to mobile services without your consent. ( ABC News: Nick Wiggins )

How much do they cost?

The charges vary, and may be a one-off charge, or more typically, a weekly or monthly fee.

The Australian Communications and Media Authority (ACMA) says one-off charges can be up to about $20, while subscription services start from about $5 a week.

In 2017 the Australian Communications Consumer Action Network (ACCAN) estimated Australians shelled out around $20 million on such unsolicited "services".

Loading...

How many people have been affected?

Probably millions.

ACCAN's 2017 survey estimated 1.9 million adults received unexpected charges on their mobile phone bills through unsolicited SMS services.

Last year Telstra refunded more than $9.3 million to 72,000 of its customers it misled after they unwittingly subscribed to premium content on their phones from third parties.

At one stage the telco was receiving 10,000 complaints a month from customers who were paying for a service they didn't want.

Telstra was also ordered to pay $10 million in penalties for making false or misleading representations about third party content.

Optus has followed suit, admitting to making false or misleading representations to customers after the ACCC launched proceedings against it.

It paid out $12 million to affected customers, while third party providers forked out an additional $19 million to Optus customers.

How do I make it stop???

ACCAN recommends you cancel the subscription in the account settings section of the website — that's if your unsolicited "service" provider has given you a website link.

It says you can also reply 'STOP' to the number from which you're receiving messages — which usually costs 25 cents — or call the content provider's helpline, which ideally should be listed in the messages you're receiving or on its website.

But you'll still be charged for any content you received before you unsubscribed.

If you still can't solve the problem, contact your telco for advice.

Importantly, you should also ask your telco to block all third-party billing on your account so it doesn't happen again.

Can I get my money back?

If you were subscribed to a service without your consent, or misled about the charges or nature of the services, there's good news.

Australian telcos have paid out millions of dollars related to direct message services. ( ABC News: Nick Wiggins )

According to ACMA, you may be entitled to a refund.

This can be in the form of credit added to your mobile phone account, or a cheque in the mail (yes, apparently such things DO still exist).

What can be done about it?

The good news is the major telcos have made changes, and ACMA, the telecommunications regulator, is also onto it.

In March last year Telstra stopped offering premium direct billing services, while Optus has also clamped down on the practice.

And ACMA is reviewing the Mobile Premium Services Code to include direct carrier billing.

The good news is according to ACMA premium mobile services are now on the wane in Australia and complaints to the Telecommunications Industry Ombudsman about them are few and far between.