This article is more than 1 year old

UK mobile number porting creaks: Arcane system shows its age

Any, sorry, many ports in a storm...

Comment Problems with the way the UK has implemented mobile phone call routing are emerging as an architecture designed for a small volume of calls struggles under the weight of usage.

When you call a mobile and get a "number unavailable response" – without the call going to voicemail – it may be a much more deep-rooted problem than just poor coverage.

We saw an issue where calling a number on Vodafone from Three always failed, of course it took a while for it to dawn on anyone what was happening. You don’t know when someone has tried and failed to call you, and we are all so used to mobile calls failing we just write it off.

It transpired that ALL calls from Three to that number on Vodafone failed. Texts got through and the Vodafone customer could call Three users. Initial calls to Vodafone and Three tech support led to each blaming the other. They were both wrong.

It took some research, but only building a theory as to what was going wrong, and making sustained attempts to talk to Three support in order to get through to someone senior and technical enough to understand the issue got the problem resolved. The ticket raised by the Vodafone customer never got "actioned".

The root of the problem was that the number in question had been ported. UK number-porting is a chummy club between the UK operators and the US company Syniverse. If you want to join the club you’ve got to pay high rates for access to and maintenance of the APIs. It’s for the big boys and they don’t want the first years playing.

While Syniverse holds the database of which number has been moved to which network, that’s not used for call routing. Instead the system works on who originally issued the number. 07802 – that’s a BT Cellnet number, 07956 came from One 2 One and in our case the 07973 was originally with Orange. Note none of these companies still exist in their original form or under their original owners.

So when we dialled 07973 from the Three number, the first place Three went to look was EE/BT, the current keeper of Orange numbers. BT then redirects the look-up to Vodafone, which holds database of where it expects the call to come from. If the call comes from somewhere else the receiving network rejects the call. We suspect that when the 07973 number, first issued in 1995, had been ported from O2 to Vodafone, BT didn’t update Three’s records.

We've asked BT and EE for comment on the issue.

The mechanism was devised in the days when Mobile Termination Revenue was important. The caller was paying Three 25p a minute for the call, Vodafone would have wanted a slice of that, perhaps 5p, for the on-going handling. The early internet service provider Freeserve built its business on fixed line call generation revenue.

Knowing to whom the MTR bill should be sent was important. These days MTR is – depending on where you sit in the order of things – either tiny or non-existent. Of course a receiving network still needs to know where the call comes from, particularly when there is roaming revenue in the mix, but the need for porting to:

  • update the Syniverse database, the original issuer of the number,
  • update the database for the network porting out – which may or may not be the same as the original issuer
  • and update the network where the number actually lives...

is overly complex. It’s not what happens in other countries.

The mindset of operators not wanting to let go needs to change and call-routing should be handed over to a central organisation, probably Syniverse, which does the porting under the auspices of the GSMA.

This is of course where Ofcom should step in and the regulator has been proposing a system whereby customers can port much more easily, using text to request not just a PAC code but an immediate port so that you could leave the shop with your new phone working on the old number. It’s not a bad idea, just an unworkable one. The whole system runs as an overnight batch.

To give Three some credit, once we’d found someone senior enough she was genuinely interested in the problem, took ownership and got it sorted, but no normal mobile user is going to have the perseverance to work through the issues or have friendly network engineers they can talk to. Instead they will just give up calling that particular person, which isn’t what mobiles are supposed to be about. ®

Simon Rockman is a former Vulture and the founder of Fuss Free Phones, the personal mobile phone network which uses telephonists to make using mobiles easy. Failed number ports are his daily nightmare.

More about

More about

More about


Send us news

Other stories you might like