that the user makes is routed to an Interactive Voice Response (IVR) device that announces to the user that the account balance is low and suggests they add funds to the account so their service is not interrupted. When the user's account balance is depleted, the service is suspended until they added funds to their account. If the user's account balance is depleted, all call attempts are routed to the IVR. These patents expired in 2010 and 2012 respectively. The prepaid service was sold to Metro Mobile in June 1989, and was implemented in November 1989. The prepaid service was also sold to carriers in Mexico; Celcom in 1994, and implementation took place in Monterrey, and to Telcel, where implementation began in November 1997 and production took place beginning in April 1998. Ericsson also became a partner in the prepaid service; a Memorandum of Understanding (MOU) was signed in June 1997 and the final agreement was signed in late 1997. The announcement was made on January 26, 1998 (or listen to it). Prepaid service enabled carriers in third world countries to add subscribers without having to print monthly statements or having an accounts receivable department, and gave them the ability to add subscribers without concern for their ability to pay their bills.patent holder). In 1996 MTN became the first mobile operator to introduce a prepaid cellular service in Africa, popularizing "pay as you go" in emerging markets. The first Prepaid card was called "Mimo" and was launched by TMN, the mobile phone operator of Portugal Telecom, in September 1995. In 2006 Swisscom celebrated ten years with its product and service "NATEL® easy" which also holds a patent on "Prepaid mobile subscriber identification card and method implemented thereby". Versus postpaid Advantages A prepaid plan may have a lower cost (often for low usage patterns e.g. a telephone for emergency use) and make it easier to control spending by limiting debt and controlling usage. They often have fewer contractual obligations – no early termination fee, freedom to change providers, plans, able to be used by those unable to take out a contract (i.e. under age of majority). Depending on local laws, they may be available to those who do not have a permanent address, phone number, or credit card. This makes them popular among travelers and students away from their hometowns. Additionally, they are popular with parents who wish to have a