I'm trying to use a USSD and I need to enter alphanumeric characters in one of my responses but my phone only offers me the number pad.
I read online USSD supports alphanumeric characters but I've only ever seen USSD menu require numbers as a response.
USSD code is always represented by numbers. Refer to the attached image, on the regular dial pad, numerical number 2 could represent A, B and C. Other numbers represent respective characters as well. For example, for AT&T, you could send *3282# to query data usage. And you could say you sent *DATA# as USSD. USSD sends numerical string on-air interface only.
https://www.wikihow.com/Run-a-USSD-Code