Yep, Virgin Mobile customers have to learn more about T-Mobile services to use as a back-up that's for sure. I didn't know that about T-mobile and GSM carrier. I'll have to study more about them and maybe use them as a backup myself! Thanks!
The "trick" with GSM phones is that your account information is kept on a SIM card that you can remove from the phone. With most GSM providers, you can remove the SIM from one phone and (as long as the phone is not locked to a different carrier) put it in another and have the phone work. In fact, some people keep two phones, they use one for normal, daily use and another, older phone, if they are going to be exercising, doing manual labor, or another activity where there is a higher risk of damaging the phone. They just swap the SIM card as needed.
Their are two major US GSM Networks, T-Mobile's and AT&T's. The one thing to watch for, their networks use different frequencies and not all GSM phones can handle both sets of frequencies. AT&T uses 1900 Mhz for their 3G/ HSPA+ "4G" service, T-Mobile uses 1700 and 2100 Mhz for theirs. AT&T phones will still get 2G speeds on T-Mobile, even if they don't work on 3G. Phones like the Nexus 4, purchased from Google, work with both frequencies, as well as most T-Mobile phones. AT&T phones typically only work on the 1900 Mhz frequency. T-Mobile has been refarming the larger US cities so that you can get T-Mobile service on AT&T phones.
This map shows the cities where people have reported 3G works on the 1900 Mhz frequency on T-Mobile. AT&T LTE should work on T-Mobile's LTE (where available), as AT&T in some areas uses the same frequencies for LTE.
While there are only two major GSM networks, there are several GSM MVNO's. Some of the better deals are: T-Mobile, which has a $30 plan with 100 minutes talk and 5 GB of up to 4G data and a $70 unlimited talk, text, data (unthrottled). T-Mobile's $70 plan is available both pre-paid and no contract postpaid and, if you have a family account (postpaid only) with multiple lines, each line discounts the cost of the plan (to the point that with 5 lines on the account, you pay only $42 per line for the $70 plan ($210/month total if all 5 lines are unlimited). Straight Talk is $45 for unlimited talk, "unlimited" data (typically cut off or throttled around 2 GB). Solavei is $49 for unlimited talk and up to 4 GB of 4G data, they also have data and voice roaming; they also will discount your monthly rate for having referred users that are current subscribers. There are the various Straight Talk sister companies (subsidiaries of TracPhone) such as Simple Mobile and Net 10. Most MVNOs are currently using the T-Mobile network, it seems AT&T has been getting rid of their MVNOs.
Last, when talking of 4G it can mean two things. First, there is HSPA+, this is an extension of the GSM 3G standard that runs at 4G speeds. Unlike WiMax, since it is merely an extension of the 3G service it does not require a separate antenna. Additionally, the phone will connect to any 3G tower (regardless if HSPA, HSPA+ 21, or HSPA+ 42). There are typically two speeds you'll see, HSPA+ 21 and 42. First, AT&T's network only supports up to HSPA+ 21, T-Mobile's supports up to HSPA+ 42. Secondly, some phones (for example, the Galaxy Nexus and the LG L9) only support HSPA+ 21, whereas phones like the Nexus 4 support HSPA+ 42. Users with HSPA+ 21 can see speeds in excess of 10 Mbps, typically getting at least 5 Mbps with a good signal (in areas that HSPA+ is available); with an HSPA+ 42 phone you can see speeds in excess of 20 Mbps, with speeds around 10 Mbps common in areas with a strong connection. T-Mobile is just rolling out LTE, with the first cities going online in March -- you can see what areas are having LTE rolled out using the
Sensorly map (with "T-Mobile - 4G" selected).
Hope this helps.
