I don't think Toshiba FYI is going away this year. Tech support is going to be around until 2021. I would expect FYI to be up at least that long.

When you changed the Voicemail port DNs, did you log into the voicemail and change the pilot extension number to 601?

I don't know what integration you have on the CIT 100, but if it is DTMF then it doesn't matter what the extension numbers are for the voicemail ports. With the CTX28 and CIX40, along with SMDI integration the port numbers in the CTX/CIX have to match the voicemail system settings.