In the last few years the pre-paid services had been developing dynamically due to telecommunication companies. Nowadays almost every company that provides electronic and communication services, deals with pre-paid selling. Conventionally clients have to buy a plastic card - that function as a stock - before the service consumption/ usage. This plastic card should be activated before start using the services and it means that the secret code and the client have to be related to each other. (scrape, then enter the secret code (numbers) and send it with the help of the mobile phone). This procedure is usually carried out via phone or Internet. Due to the relation between client and the secret code, the owner of the card is entitled to use the services. The essential thing in pre-paid services that the client pay in advance for the services that he/she would like to use and in this case there is no delay payment and the planning of liquidity of the services provider is easier. A pre-paid service is for example the GSM phone top-up. The consumer does not pay for a plastic card, but pays to top-up directly and immediately to the service provider. The information above shows the fact that the plastic card has no other function just to provide the secret code which with usage of the adequate service can be activated after buying it. The mobile Online service provides this function electronic, avoiding problems and costs connected to plastic cards.