you are right - modem calls have different holding time patterns.
however, samples of large modem pools don't (yet) show them to be
many hours long. (about 4x a normal phone call if I correctly remember
the last numbers I saw)
but if they are really concerned about holding times, howcum they
price "teen phones" even cheaper than ordinary??? those lines
certainly don't exhibit classic 1MB distributions (and those
don't exhibit them anymore, either).
no, they have simply identified someone whom they think has no
alternative to just bleeding more. Ah, the perks of the monarchy.