Hi @Randi,
Kindly note that Microsoft Q&A forum mainly focus on general usage questions about Teams.
Since this question is more about license, I would suggest posting in the Microsoft Community for better support.
Based on your requirement, since users won't make a large amount of calls so the Pay-As-You-Go plan should be the most economical one.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.