Viettel Telecom, a mobile network operator in Vietnam, and mopay have signed a strategic carrier billing partnership, according to a press release. The companies said the pact will enable mopay's international merchant portfolio to allow Viettel's 58 million customers to transact with mopay and charge digital purchases to their phone bill.

The companies said in a statement that three factors brought mopay and Viettel together: the sheer size of the local Vietnamese mobile market, which has the eighth highest number of mobile phone subscribers in the world; the steep growth of smartphones by more than 156 percent over the last three years; and the openness of Vietnam's leading carrier to fully embrace the carrier billing opportunity. California-based mopay will introduce its platform with a direct integration into Viettel's billing platform to ensure access to commercial deals currently available through its merchant base, the company said in a statement.

When purchasing a digital or virtual item online, consumers choose mopay as their payment method, as the company only needs a verified mobile phone number to bill the requested amount. No registration or further information is needed. All user interfaces, such as PC screens, tablets and mobile phones, are supported in order to make the payment method adapt to different usage scenarios, according to mopay.

"Vietnam is a very vibrant country where you can literally feel how quickly this market is evolving," Ingo Lippert, CEO of mopay, said in a statement. "We feel privileged to team up with Vietnam's largest mobile network provider, Viettel, to take mobile payments to the next level."