foen is made by sun-dive. There is no company office and no call centre; there is a person, and a public repository.
There is no email address here on purpose: a published address is a spam magnet. Messages go straight to the operator and nowhere else.
Problems with the software
Open an issue at github.com/sun-dive/foenx/issues. That is where fixes are tracked, and anyone can read what has been reported.
Advertising and business
Use the form. Direct placements on the idle screen are available to businesses whose products suit a free telephone.