Wireless carriers T-Mobile    and Verizon are reportedly teaming up to invest $100 million more in Isis, a joint venture that turns smartphones into mobile wallets.

Called Isis, the project was launched with AT&T in November and will let customers pay for goods and services with their mobile phones. This newest investment could help Isis compete with Google Wallet, a similar venture rolled out by Google in May.

When it debuted, Google Wallet had already formed partnerships with Citi, MasterCard, Sprint and First Data. Though it faces some limitations (i.e. only one carrier in the group), Google has said its service will be ready for launch much sooner than Isis.