Instant PINs, virtual calling cards it mostly credit card based and are predominantly delivered over the internet. They are nearly always prepaid and come mostly in low denominations. In each case no credit card is delivered and you will recieve a set of access numbers and identity or PIN codes. These cards normally are a one off purchase and expire. You need to buy a new one which will come with new codes if you wish to use the same calling card vendor again. Typically the time based phone cards come in steps of 100, 300, 600, or 1000 minutes. Money based calling cards start at $3 and go up to around $100. When you make a call, the total price of the call which is frequently made up of several elements is accumulated and the remaining value on the card is reduced by the cost of the call.
In a slightly different form, this technology has become so advanced that it is now possible to buy a prepaid calling card which is actually a miniature disposable cellphone. This card comes preloaded with airtime and when the time is used up the card is discarded.This form is particularly suited to foreign travel where you can make use of the local mobile phone system at local rates for short duration.Permanent PIN instructions | Permanent PIN calling cards