Ofcom is to ban mobile phone firms from charging customers who call 0800 numbers.
Currently, mobile users pay up to 40p a minute to dial the numbers, which are free to call from a landline and are used by many public bodies, including councils and the NHS.
The regulator is due to ban the practice within weeks and introduce rules to clarify other charges for so-called non-geographic numbers beginning with 08 or 09.
Such changes will help reveal the true cost of taking part in phone votes for reality TV shows such as Britain’s Got Talent.
Phone companies will be required to inform customers of the standard cost of calling an 09 premium number, while TV companies running the polls will have to show additional charges on-screen.
Ofcom is also planning to clear up the confusion surrounding the cost of using 118 directory enquiry services.