pay-per-
prefix
ukusused toformadjectivesthatdescribeasystemofpayingonly for thetime,partof aservice, etc. that you use:
Withpay-per-clickadvertising, youpayeachtimeawebuserclicksintoyourwebsite.
You cancallmobilephonesbut notpremium-ratenumbersand thepriceis 6.50eurospermonthpluspay-per-call.