MobiMatter

MobiMatter operates as an eSIM marketplace where you build custom packages starting at $0.7 per gigabyte. Major US carriers including 5G and 4G LTE are available, and the company provides 24/7 phone support.

Best if you want to pay exactly what you use without preset plans or overpaying for unused data. The low per-gigabyte rate works well for light users or those visiting for just a few days.