More than 1,000 surgeries are still charging patients more than 40p a minute to make a call, a month after they were told to stop.
Doctors should no longer use the high cost 0844 or 0845 lines under guidelines that came into force at the beginning of last month.
Calls to these numbers can cost as much as 41p a minute from a mobile phone, with GPs keeping part of the income.
Campaigners say that some patients phoning to book an appointment or chase up test results are sometimes kept waiting on the line for 20 minutes, working out at £8 for a single call.
The clampdown followed a Government review which heard complaints from more than 3,000 members of the public.
In September 2009 the Department of Health announced that GPs would be banned from using the high rate numbers, and the guidelines came into force on April 1.
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