Being forced to convey things like addresses, phone numbers, credit card numbers, etc by voice instead of text can be incredibly painful, and of course it gets worse with poor quality connections, accents, non-native languages, etc.

I almost wish there was some low-tech thing for sending text in-band in voice calls, like DTMF but for all ASCII characters, or some 75 baud protocol / tones so you could be like 'Ok, I am sending my name / email / account #. <sending> See it on your screen? great! screencap it... copy and paste it into your app now, etc!'