I see.
You have a couple of choices. Some of this might be region specific but I think for the most part would be accurate.
If you don't have any IVR licenses (as in any level of) then you need to purchase the premium port on version 7- IF version 7 parts are still available in your region that is. I don't think so though.
You can upgrade to release 8 and then purchase IVR ports (note in release 8 IVR port levels are no more, they are just called IVR ports). As a side, if you own MiCC Enterprise it will convert to MiCC Contact Center and some "IVR" ports are included free of charge. Note I put "IVR" ports in quotes since technicaly they are called Messaging and Routing and are free with the Contact Center base (there is also a workgroup version and it is not free in that base version). Messaging and routing won't do what you want though so you need the full IVR port.
If you do have IVR ports on release 7 then anything above advanced I think will convert to full IVR ports in release 8 so you wouldn't have to purchase them again.
Ok that is a lot and probably confusing. Best you chat to a Mitel rep in your region