Can't program conditional call forwarding

I am trying to program a number for conditional call forwarding. However, the system is not allowing me to do so. Here are the details:

I recently deactivated Videotron's voicemail on my Pixel 2XL. Until that time, I was able to program a different number for conditional call forwarding (CFW). Now, everytime I try to activate CFW, it gives me an error message "connection problem or invalid MMI code" or "Call settings error: Unexpected response from network".
I have call forwarding as one of the options I chose for my plan. My phone gives me the option of changing the number, but the system gives me the above error message.
I just got off the phone with tech support (Videotron). The person was telling me at first that Videotron does not offer CFW (although that is basically what the voicemail option is). When I explained that it used to work until I deactivated Videotron's voicemail, he then me that CFW is only available for those who have voicemail activated.
Do I have any options (aside from subscribing to their voicemail that I don't use)?