Currently Office 365 GCC customers are unable to use communications credits in order to leverage Pay-per-Minute Toll-Free audio conferencing for Teams or SfB even though Microsoft does have an Audio Conferencing Pay-per-Minute GCC $0 SKU available to O365 GCC customers. Please enable the use of Communications Credits so that GCC customers can leverage Toll-Free pay-per-minute audio conferencing as part of their Unified Communications strategy.