I have been called by a variety of restaurants and drivers 7 times since March 2023 while using Deliveroo - who all came through the same London phone number.
I don't even live in London.
A search online for the number (020 3871 3395) shows that others have been called by both drivers and restaurants on this number. [1]
They use a proxy system where the driver has to call a standard number provided by the app and then input a code to identify the specific customer.
That's typically only available while the order is in progress.