The Communications Ombudsman has called for an end to shocking mobile data bills, focusing in particular on purported "unlimited" offers from providers.
Unlimited offers don't genuinely mean users can download as much as they want without extra charge, although many don't understand this and rack up massive bills.
"This is an emerging problem which we think could cause real consumer detriment we want mobile phone companies to take action before it becomes more prevalent," the Ombudsman said.
If a welcome letter, which clearly explains the limit, isn't read or is ignored, there is nothing we can do to help.
"We are speaking to mobile operators and asking that they take our advice to be very clear about the limits on the packages they sell, and to take quick and effective action to stop large unexpected charges building up and to take steps to tell customers before they exceed their limit."
The Ombudsman is also recommending users are more vigilant when they sign up to "unlimited" deals.
"Consumers must make reasonable efforts to understand the limits of the package they are on and take steps to understand the terms and conditions of what they are buying, before they sign up to a fixed contract," the body added.
"If a welcome letter, which clearly explains the limit, isn't read or is ignored, there is nothing we can do to help."
Given how much data consumers are using these days, transparency from providers is becoming more of a talking point.
Mobile operator 3, one provider offering an "unlimited" deal, recently revealed 97 per cent of its traffic is data. The company claims its all-you-can-eat data plans for smartphone users are "genuinely unlimited."
The Advertising Standards Authority (ASA) has decreed that it is fine for operators to use the term "unlimited" in marketing efforts as long as the consumer is informed of the limits in some way.
