MFS, a joint venture between Telefonica-owned carrier Vivo and MasterCard, has expanded its Vivo Zuum mobile payment service to São Paulo, the biggest city in Brazil. The service lets users make in-store payments via USSD, pay bills, transfer funds between Vivo Zuum accounts, top up prepaid airtime and withdraw cash from MasterCard ATMs. Vivo Zuum is also available in Salvador, Belo Horizonte, Porto Alegre and Aracaju.