As 5G broadband networks expand across the country and more phones are released that can connect to those networks, wireless service operators have been vying for dominance of the market. But just because one carrier claims it’s the best, doesn’t mean everyone's going to agree with how it came to that conclusion. T-Mobile's finding that out the hard way, as the BBB's National Advertising Division tells it to stop advertising it has the "most reliable 5G network."

These claims are most recently based on a report from German research firm umlaut which analyzed multiple carriers' 5G coverage, subscribers' ability to connect to 5G networks, and download speed.

AT&T decided to challenge this language at the National Advertising Division (NAD) of the Better Business Bureau, and the NAD has reached a decision. It recommends that T-Mobile no longer make claims that its 5G network is the most reliable, even with the qualifier that this conclusion was reached by an independent company.

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At the root of the NAD’s decision are two issues: what constitutes reliability and which data was used. The report based its conclusions on coverage and speed only. The NAD directly addresses this, saying that there’s more to being reliable than just these two metrics.

Regarding the data used to establish those speed and coverage metrics, part of the report’s methodology measured how consumers used 5G as a supplement to existing 4G networks. The NAD concluded that T-Mobile can’t make claims about its 5G network based on data from 4G connectivity.

For its part, T-Mobile has said it “is disappointed with and will appeal NAD’s decision.” That decision will be made by the National Advertising Review Board. Although T-Mobile is not legally bound by the NAD's criticism, the body reports all recalcitrant advertisers to the Federal Trade Commission, which is in charge of regulating advertisements.