Conduent is to be responsible for vehicle identification, payment processing and account management for drivers using the Dartford Crossing over the River Thames near London.
National Highways, which manages England's motorways and A-roads, says Emovis will continue to issue and handle enquiries for penalty charge notices (PCNs) for the Dart Charge payment system.
It adds that the changes to the free-flow toll scheme will make Dart Charge "an easier and more accessible service".
Around 160,000 vehicles make the crossing each day; account holders will need to re-validate their payment cards from 28 July 2023 or risk receiving a PCN.
National Highways says it has "written directly to affected customers" and will issue "further reminders in due course, together with messages on social media to highlight the need for customers to take action on their accounts".
Helen Watkinson, Dart Charge head of road user charging, says: “We have worked hard to design a customer-centric service with the new suppliers, really putting the customer at the heart of our design."
