Lunch Time Teaser – 04

Welcome to this month’s lunch time teaser; A practical RA problem, which is solvable within a 30 minute lunch break.

The challenge

An audit using a test call generator showed in some circumstances it is possible to make voice calls without being charged. The CFO asks you to look in to it and tells you to report back with your findings within 30 minutes.

There are four sets of data available to you, as outlined in the diagram below.

The file from the provisioning system contains the “customer’s name” and the “MSISDN”.

The file from the HLR contains the “IMSI”, the “network status” (NWS) which has the following definitions:
A = Active
B = Barred on the network
C = Cancelled on the network

And the “service type” (SER_TYP) which is a binary flag with the following definitions:
00 = Incoming voice calls only
01 = Outgoing voice calls only
10 = Data calls only
11 = Voice calls and data

The file from the rater contains the “MSISDN” and the “tariff plan” information.

And the file from the billing system contains the “customer’s name” and the “IMSI”.

The audit found that “active” customers on the precept 250, 500, and 750 tariffs, and with a “service type” = 01, could make unlimited free calls. The challenge is to identify the name of the customer(s) who this relates to, so your company can send them a back-dated bill.

Please email your answers to  – the answer will be revealed in two weeks time, along with the names of the first three correct answers.

Lee Scargall
Lee Scargall
Lee is a senior risk management professional. He has extensive experience of managing both ERM and RAFM teams in telcos around the world, having worked for Ooredoo Group, Cable & Wireless and T‑Mobile UK.   Lee earned a PhD in Electrical and Electronic Engineering from the University of Newcastle upon Tyne, UK, for advanced research in to 3G video-telephony.