If your provider does not have a gateway address listed here, most providers use one or multiple of the 5 largest networks in the US: AT&T, Sprint, T-Mobile, U.S. Cellular, and Verizon. T-Mobile recently purchased Sprint, but Sprint’s network is still active. If a provider isn’t listed here, you could find out which network is being used by that provider (usually listed under cellular network settings on the phone) and test the gateways above for those networks. AT&T and T-Mobile are used for GSM phones and Sprint, U.S. Cellular, and Verizon are used for CDMA phones.