Call recording app (Bluetooth)

I'm trapped on a phone with no unlockable bootloader. I need to be able to record calls, I do have an app that works ACR phone but... it won't capture anything but my voice on the call when connected to bluetooth, anyone have any idea of an app that works, a potential way to fix this and or a extra app I can add to grab that audio if need be, I'm in a bad legal war with family and need to be able to record the calls, but holding a phone to my head for hours during conversations is a nightmare.