used to work in a company that build and implemented BSS/OSS system for major telcos (including the one that you mentioned). I can totally see that high level

used to work in a company that build and implemented BSS/OSS system for major telcos (including the one that you mentioned). I can totally see that high level pricing for a packages is modeled globally and exposed to sales team while taxes are implemented only in billing system, because its "zip code" specific.