Premium Rate services are standard services in all mobile networks. Higher (Premium) payments are charged to user's bill for sending an SMS or MMS. This mechanism is very often used as a mean of payment, a method of content distribution, registration to some contests or lotteries or a dialogue with clients medium.
User has to send SMS or MMS to a given four- or five-digits Premium number (e.g. 7114 or 72412), usually with a given text (short-code). While sending SMS or MMS, Premium payment is added to user's bill by the mobile operator. Depending on the country and Premium phone number, sending one Premium SMS or MMS can cost from a few Eurocents to a few Euro.
When planning the SMS campaign, you have to remember, that Premium services can be only a piece in the whole campaign - SMS mechanism has to be promoted via other media, consumers must be informed what short-code they have to send to what Premium number.
WAP-Premium also belongs to the group of Premium services. Payments are calculated in the same way, as while sending Premium SMS/MMS, but the user has to click on a WAP link instead of sending the message.