necro'ing this because i had to deal with this garbage again and the solution wasn't the ol' reliable
valve in all their thoughtful helpfulness has decided to remove your own entry from the mute interface which means phantom's post doesn't work anymore, other posts online will tell you to use "cl_mute_all_comms 0" which just turns off chat muting
open voice_ban.dt in notepad++ (pretty much anything less sophisticated than sublime text, which will try and open the file in binary format), ctrl+f your steamID3 (ex: [U:x:xxxxxxxx]) and delete it and the 18 null byte padding afterwards
pain in the ass