Here are a few of the larger more reliable VPN services.
Fantastic 3G 4G 5G coverage area tool and Internet speed test
This is a fantastic tool I just found!
You input an area, and the carrier, and it shows you on a multi-colored map where the coverage is and at what speeds it’s available at.
On the main page, there’s an Internet speed test tool, and a very good one! It shows latency, download, and upload speeds.