The year-old Surface Pro 9 now includes 90 days (or 30 GB) of free 5G service, courtesy of T-Mobile. This free trial is only available in the U.S. and requires a Surface Pro 9 with 5G tablet—the standard Surface Pro 9 does not have a cellular modem and cannot connect to 5G networks. You do not need to be a T-Mobile customer to redeem this trial.
Source : Surface Pro 9 Owners Get 90 Days of Free 5G Service