Documentation

Prices are published as revisions. Each revision is immutable once published, so "what was the price on 3 March" has exactly one answer.

A price change is not retroactive

A period is rated with the prices that were in force when that period started. Publishing a new price today does not re-price a month that was already running, and re-rating last month produces the same number it produced the first time.

Currency

Prices are in Toman. Where a US-dollar figure is shown, the conversion rate is pinned in the same published revision rather than read live — otherwise re-running last month's bill would produce a different amount than the one you were charged.