Yes, it is all possible. I'd want to phase out the TCL number & get all your customers back calling on the old Telecom number. I think if it were me in this situation I would get an extra VFX line & port the TCL number onto it. I would answer it for a while & tell each caller that the line is being closed & they should use the Telecom number next time they call. Then after a period you could just leave it being answered by a recording announcing the new number. With VFX voice mail you can give people the option of being transfered when they press 0. So you could leave an announcemnet that says something like 'Thanks for calling bla bla, the number you have dialed is no longer in use. The new number is XXX-XXXX, you can be connected to the new number by pressing zero now.' Then you can just repeat it several times (using copy & paste in a audio editing application). VFX has an 'Intercept User' function that you might be able to use here, but I can't figure out how to configure it.

I had to change my business number once & it took me about 3 years to completely phase out the old number.