Hi. I purchased Zoom modem model 4598. I bought it to work with Voicent BroadcastbyText through my T-Mobile SIM card. I tried it and it is not working, but it works if I use my AT-T SIM card. I thought it was because of the defected SIM card, but I replaced it twice at the T-Mobile store and still gave the same result. Help?

Zoom 4598 modem only supports frequency band of 850, 1900, and 2100MHz, while T-Mobile sends out data through frequency bands of 1700 and 2100 MHz. However, T-Mobile GSM card will still work depending on your location. If the location of your SIM card is near a cell tower that sends out 2100MHz, then you should be fine. But if you’re unlucky, there’s a chance that your T-Mobile card would not work as your location might be sending data through 1700MHz frequency band.

This information also holds true for AT-T 4G LTE technology. 4G LTE sends data through 700, 1700, and 2100MHz frequency band. Although, AT-T’s 2G and 3G GSM cards all well supported by Zoom 4598

Whatever card you have or location you are in, you should purchase a mobile broadband modem that supports the frequency bands that you are using. Hope this helps