top of page

Fonbnk: A DeFi dApp using mobile prepaid airtime credits as an onramp to Web3 for the emerging world

Fonbnk was started as a bet between the founder, Chris Duffus, an experienced Fintech entrepreneur, and his brother-in-law who recently returned from a vacation to Kenya. The wager involved an unused Safaricom SIM and how Chris might sell the value locked in the unused SIM card back to an airtime reseller in Kenya from his home in Washington, DC USA. With some ingenuity, he devised a hack taking out digital ads. He was able to find a few interested parties who he invited to join a Whatsapp group and was able to sell the airtime credits using the Safaricom SIM card and mPesa account. From here Fonbnk was born.

Path to Celo Camp

The first rule at Fonbnk is you don’t talk about crypto! Since its inception in 2020, the company has trading activity across all the leading Sub-Saharan African countries, generating over $5 million in Gross Airtime Transactions, nearly 100k transactions and over 50k new wallets. Our primary objective has been improving the user experience and accessibility. A primary product objective for the Fonbnk dApp was to abstract as much about the blockchain as possible so crypto newbies would feel comfortable; no need to understand keys, wallets, etc. They just need to be able to top-up or recharge their prepaid mobile! Specifically, we needed to build on top and support an ecosystem that was mission aligned, and not only supported high transaction volume but also low transaction costs. ETH gas fees inhibit access to our customers. We read about the Celo protocol and were introduced to the ecosystem team from our advisors at Techstars Western Union, which we recently completed.

Highlights from Celo Camp Batch 4

Having participated in accelerators and hackathons prior to, I wasn’t expecting much and furthermore was ready for a boring seminar experience. Celo Camp Batch 4 was not!

Every week, the first thing on the program was the “Prosper Session.” This was a weekly meditation session led by an experienced Celo Yogi. It was awesome because it set the tone for camp participants and helped us get in the zone to be prosperous in our project. Finally, the facilitators were amazing and very organized, allowing us to maximize our participation despite it being a virtual program.

What We Built

Fonbnk ( addresses the problem of how to onramp fiat value from the CeFi world to that of Crypto and DeFi; how to get fiat currency onto a crypto wallet across emerging/frontier markets where this conversion is not readily available.

We created a decentralized, market-making dApp through which users can convert the value on their existing prepaid mobile SIM cards into cryptocurrency. This is achieved by transacting with a network of airtime liquidity providers or market makers for their respective mobile carriers prepaid airtime credits. For example, if a user in Nigeria wants to convert #411NGN MTN mobile airtime credit into $1.00 USD of ETH, a user can swap their credit for Fonbnk's ERC20 token MIN, which can currently be used to mint USDC and then be traded for ETH on select exchanges. Fonbnk currently has a business relationship with Circle Financial.

To that end, we built a simple bridge to Celo wallets from Fonbnk's dApp. This will enable Fonbnk dApp users to convert their fiat-based prepaid airtime credits directly into Celo Dollars (cUSD) from anywhere in the world regardless of their banking status. See our demo video here:


Twitter: @fonbnk



// The End

Author: Chris Duffus | Founder & CEO |

1,167 views0 comments


Subscribe to our newsletter

bottom of page