Hi rebel
This is indeed a somewhat complicated issue:
If we include this as part of the cost, we will also have to give Telkom credit for the (very useful) extra service (phone calls) somewhere else in the rating system. This will cancel the cost effect for the greater part. Also, it will complicate the rating process considerably (quantification of the advantage of the telephone service vs its cost - something outside the scope of this rating system).
Furthermore, the assumption that residential users will have a phone line in any case, ADSL or not, is plausible, and hence this was omitted as a factor in the rating process.
CB