Why you must dial 0 before most phone numbers in South Africa

South Africa uses a closed numbering system that makes it compulsory for all landline and mobile numbers to have a “0” as a prefix when dialled from within the country.

A MyBroadband reader recently asked why it was necessary to dial this seemingly unnecessary “0” when the only unique part of a number was the nine digits that followed it.

They asked whether it would not be possible for mobile networks to automate the “0” when making a phone call, to make numbers shorter and simpler to dial.

MyBroadband contacted South Africa’s major mobile networks to learn more.

Telkom explained the country’s phone numbering scheme was managed by the Independent Communications Authority of South Africa (Icasa).

“Network operators are subject to the regulatory framework which defines and requires the format — including length — to be consistent,” Telkom said.  “It defines the format exchanged between operators to ensure correct routing.”

“Random number lengths would give rise to inaccurate routing of calls, which would undermine customer experience.”

Telkom said that the current numbering system was required due to a critical number shortage that had begun to develop in Gauteng Central in the early 2000s.

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The South African Telecommunications Regulatory Authority (Satra), one of the predecessors to Icasa responsible for regulating the telecoms space at the time, published a discussion document on how to deal with the shortage in 1999.

One of its proposed changes was eliminating seven and eight-digit numbers to free up more numbers and avoid confusion when splitting up area codes.

As part of the solution, fixed-line to fixed-line calls had to be ten digits long and include the area code, which was unnecessary before.

At the time, someone within Johannesburg could dial the seven last digits of a phone number to reach a landline within the same area.

But because numbers were running out, Satra had to introduce a new area code “010” for Johannesburg in addition to the “011”.

That opened up 20% more landline numbers in South Africa by effectively doubling the numbers available in Johannesburg.

For example, where the number “290 0000” could previously only be used for one line, forcing the use of the “011” in front of the number meant it could be used again for another line within Johannesburg starting with “010”.

Phone numbers versus shortcodes

But this, on its own, does not fully explain why Satra decided to keep the “0” at the front of landline area codes or mobile numbers.

It could have revamped all area codes to start with the second number.

For example, instead of 010 or 011, Johannesburg numbers could just have “10” and “11” as a prefix.

Similarly, Pretoria could be switched from “012” to “12”, and Cape Town could go from”021″ to “21”.

But Telkom explained that the “0” prefix was necessary because it distinguished between national dialable destination numbers and shortcodes, which often start with “1” in South Africa.

These include emergency numbers, dedicated SMS lines, and mobile network contact centres.

Telkom said although the “0” prefix could be automated on customer premise equipment (CPE), that might create problems if the call needed to break out to the public switched telephone network (PSTN) or public land mobile network (PLMN).

PSTN is the formal name for the plain old fixed-line telephone system, and PLMN is the official moniker for cellular networks.

“For example, if the CPE automatically prefixes all outgoing calls with the digit ‘0’, the user connected to that CPE cannot reach the police emergency number of ‘10111’, because the network operator would receive ‘010 111’ from the CPE.”

A spokesperson for Vodacom also said that countries that had historically not followed the recommendation of a “0” prefix were now finding the need to do so.

“It is not inconceivable that further prefix numbers may be released in future, though the timing and motivation for such a change are not clear at this stage,” the Vodacom spokesperson said.

Australia, India, and the UK are some well-known examples that use a leading “0” for calls made from within the country.

In the US, the “0” is reserved for a switchboard operator that can direct callers to various types of emergency responders.

Source: MyBroadband

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