while on the 'incoming call' screen, there are 3 options: 'pick up', 'reject' and 'reject with a message'.
the last one used to work flawlessly, but it somehow stopped a couple of months ago. I swipe up on the 'reject with message' button, select the message to be sent, the call gets rejected and...no message goes out. it works perfectly fine on the stock app, but it should go without saying that I prefer Textra.