I'm pretty sure A2DP won't help you for calls – it's using the Bluetooth equivalent of TCP (i.e. it is connection-oriented and retransmit based), which is not appropriate for real-time communication.

You want mSBC support on HFP. Here's an open ticket for pulseaudio, for example: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge...