GPs were banned from using 087 and 09 numbers in 2005 because of the high cost of calling those numbers.
For a short time after that, 0844 numbers were recommended because the supplier of those numbers said they were "lo-call rate" numbers. GPs signed up in the hundreds. The new phone system is installed at zero or low cost. The phone system is paid for by the additional revenue share money paid by the caller within the call price.
It was soon realised that 0844 calls are not cheap, costing up to 12p/min from landlines and up to 41p/min from mobiles and never included in call packages. Practices started telling patients that the high call price was the fault of the caller for using a mobile phone, or for not using BT, not the fault of the surgery for signing up to a high-priced revenue-share number.
A DoH consultation in 2009 produced a large response, heavily coming out against the use of 0844 and other such numbers. In April 2010, an explicit ban was put on the use of non-geographic numbers where the caller pays more than calling a geographic number. GPs had until April 2011 to comply with the ban. This was written into their "GMS Contract".
Although this ban obviously includes 0844 numbers, GPs were told by their supplier that they didn't need to do anything as 0844 numbers are "lo-call" rate and that patients with mobile phones or using landlines with free calls to 01 and 02 numbers weren't covered by the restriction that "patients should not pay more". Statements in parliament showed that to not be true: all patients are covered by the requirement. That message never reached GPs. The BMA sided with the phone suppier and GPs continued using 0844 numbers and telling patients the system complied with government rules.
In any case, it wasn't viable for GPs to end their contracts as these contained penalty clauses of tens of thousands of pounds for early release. Most GPs therefore ignored the ban. None of them took the option of merely changing the telephone number mid-contract to one that complied with the call costs requirement.
03 numbers have been available since 2008. These offer the same call handling as 0844 numbers but cost the same to call as 01 and 02 numbers. When GPs use 03 numbers, the practice has to pay to handle the call queueing, rather than the patient paying for it. Ofcom do not allow 03 numbers to have a Service Charge or be used for revenue sharing schemes.
The phone company continued to sign up more GPs for a further three years after the April 2010 ban started. None took the 03 option. They all went for 0844 numbers.
In April 2013, NHS England came into existance and stopped a number of GPs who were just about to activate 0844 numbers from doing so. NHS England branded the use of 0844 numbers as a "breach of contract" and promised to "take action" on this abuse.
The high call price of 0844 numbers was exposed multiple times in the Sunday Mirror, Daily Mail, and others, eventually causing the phone supplier to announce they were going to stop selling these numbers to NHS related services on new contracts. It was also revealed that call queues could be half an hour, costing a caller on a mobile phone up to 12 pounds.
There are about a thousand practices still using 0844 numbers. They all need to revert to 01 or 02 numbers or change to 03 numbers (should have been done by April 2011) to comply with the GMS Contract.
GPs complain about the high cost of ending their phone contracts. They have no need to end them. The "03 number" option has been available for more than five years. The GMS contract actually tells GPs to "vary the arrangement" for their phone services in order to comply with the call costs requirement.
Everyone is waiting for the next step. Since the 0844 usage is clearly a breach of contract, NHS England could take legal action against the remaining cases if they chose to do so.