How do I set up toll free numbers for Teams? / help with audio confereence

CarlosMtl Yes, the Microsoft shared phone numbers are assigned automatically, and there is no additional cost for using them (other than what the phone company may charge the caller, e.g. long distance).

No, you don't need Phone System to get a toll-free number for Audio Conferencing. As stated at the link you shared, the number of toll-free numbers you can request depends on the total number of Phone System and Audio Conferencing licenses you have. If you have zero Phone System licenses and one Audio Conferencing license, you can get up to five toll-free numbers. You will only need one toll-free number, however, as it can be shared by all of your users with Audio Conferencing licenses.

To be clear, you will need to purchase Communication Credits as well, to cover the per-minute charge for any calls to that toll-free number.