Calls to numbers starting 0800 will be free from all phones under proposals published by Ofcom.
The telecommunications watchdog wants these numbers to be free from landlines (as they are now) and, crucially, from mobiles too (see the 0800 Buster guide for a loophole on how to pay nothing now).
Calling 0800 numbers from a mobile can cost 40p a minute at present even though they are often advertised as a freephone number.
Ofcom also wants to make the cost of calls to 03, 08, 09 and 118 numbers clearer.
These are used by charities, Government agencies, directory services and customer service lines. Research shows callers paid £1.9 billion to dial these numbers last year.
Calls to 0800 will be free from all landlines and mobiles.
Calls to 01, 02 and 03 numbers will be charged at 'geographic rates', which are among the cheapest.
Calls to 07 numbers will be charged at mobile rates.
Ofcom will introduce a cap on 'business' and 'premium rate' numbers, though the values have yet to be decided.
Calls to 0843/4/5 and 0871/2/3 will be charged at business rates 090, 091 and 098 numbers will be charged at premium rates.
The price of 118 directory enquiry services will be clearer "potentially leading to cheaper calls".
A consultation on the proposals will take place and Ofcom plans to introduce the new rates over the next two years.
Ed Richards, chief executive of Ofcom, says: "There is clear evidence of widespread uncertainty and confusion about the cost of calling these numbers. Consumers need to have far more transparency about the price they are going to pay for calls so that they can make more informed choices and so competition can work more effectively.
"Making 0800 free from a mobile and giving people clarity about what they are paying for will improve transparency, improve competition and enhance trust in these important services."
Hannah Bullivant, telecoms specialist at Consumer Focus, says: "We welcome moves to simplify and standardise non-geographic numbers such as 0800 and 0845 - these changes are long overdue.
"For too long consumers have faced a bewildering amount of different phone numbers, all charged at different rates. It's simply unfair that someone phoning a number that is free from a landline can pay up to 40p a minute when calling by mobile."