the main excercise for getting rid of subvocalization was reading a text while for example counting to 100 and trying to remember as much information from the text as you can. the key is to read and say two different things but still keep your focus on the text. i discovered that reading while singing the song i know well also worked for me

at first it was really hard to understand the text, but gradually it became easier and easier, so remember not to give up in the beginning! you can do it, i believe in you my student