Teams calling, if not using an SBC, requires the same licensing on an IPoffice as using User portal. There is an Avaya dialer plugin for TEAMS that is free, allows click to call within teams. If they want to do the direct routing option, which uses the Teams client for Call Control/audio, and relegates the IP office to a dial tone provider, they then need E3+ Phone or E5 (this is what shows the dialpad in the Teams client)

I have had multiple customers start out with ACO or IPO, and use Teams Direct Routing for a bit, but they have all come back to ACO/IPO as the clients have the UI for what a user likes. Teams UI/Call Control sucks.

For User Portal, see if you can access the link. User guide for it:
https://ipofficekb.avaya.com/busine...%20IP%20Office%20User%20Portal_en-us.pdf