It depends on the phone and the carriers. There's a number of different types of service out there too. For instance different carriers use different frequencies (CDMA, PCS, GSM, etc) SIM cards are suggestive of GSM technology used by Tmo and ATT. If you're looking to use prepaid service you can sometimes use the phones but won't always have all the features. If you're looking for a contract service, then as cautioned before, beware of costs to change. Often the smallest thing will extend your contract. For instance, if you get a new phone, you generally get a new (extended) contract with hefty cancellation fees. You'll have to get more info from the companies, but generally speaking, Tmo will not be interchangeable with Virgin and Verizon. Tmo & AT&T are more likely to be options. Probably not answering your question, but not an easy question to answer!

I have the Moment and just plain love it. I had two Smart phones before this, and didn't care for either of them. The Moment is not difficult to learn, and the Sprint Store where she gets it should walk her through the basics of setting it up. It's got some wonderful apps that you can EASILY download for free ... including Shop Savy, which lets you 'scan' a bar code of something you're thinking of buying, and if it's in the database it'll pop up with prices of the same item near where you are to confirm whether you're getting the lowest price. Fun! I've used it for a spool of CDs and a memory card for my camera. LOL. I access both work and personal email accounts with it, and have synced my work calendar to it so it gives a little tone at 15 minutes before my next meeting. I even access Facebook with it! It sure wasn't easy to do that with my other Smart phones. Let me know if you have any other questions, I'll answer them if I can!

If you want to talk about power flow through batteries and electrical devices, I'll put it separate so as not to confuse the above. You're right - draw and pull aren't really the right words to use. They're colloquialisms I've used for years in my job. "This pulls 10 amps," etc. The best analogy, and the one that was often used in my education, is to liken the flow of electricity to that of water in a pipe. A higher amp circuit is a bigger pipe. A higher voltage circuit is like a pipe with higher water pressure. The current-using device is like the faucet you open or close. Higher pressure (voltage) and lower resistance (Ohms) are what will increase the current (amps) through the circuit. Amps do not exist until current begins flowing. Amperage ratings of power delivery equipment refer to the maximum allowable amperage the circuit or device can safely carry. Amperage ratings of power consuming equipment refer to the maximum amperage they'll carry in normal operation. To relate that to this discussion, it should now be clear why a higher amperage charger is fine: it's merely a bigger pipe that can deliver more current if needed. That doesn't mean the current will flow - the voltage and resistance will determine that - but that it can flow if needed, exactly as I started in my analogy of the night light and the microwave oven. Charging batteries is an interesting area, because you can observe what happens with a device called a Kill-a-Watt that indicates the wattage used by any device you plug into it. I have a 12-volt car battery that is one of those "booster" batteries you can use to jump-start your car if there's no other car around. You charge this battery with a supplied plug-in charger. If the battery is heavily discharged, the charging wattage will show about 14, but as the battery nears a full charge, the wattage slowly drops to about 2, and at that point you can unplug the charger. This happens because as the charger continues to supply a constant voltage, the charging current drops as the battery's internal voltage nears that of what the charger is delivering. This all occurs not as a function of any type of computerized circuitry in the charger, nor as a result of the charger's maximum amp rating, but simply because of how current flows in the battery charging process. "Smart" chargers can affect the charge rate of a battery by applying different voltages at different phases of the charging process, as batteries of different chemistry do better with faster, slower charges or other specific things, such as high voltage early and low voltage late in the charge, or whatever. Most cell phones today have charge control circuitry to somewhat counter the detrimental effects of constant overcharging, as people frequently do when they charge the phone all night while it's still turned on and they're asleep.

I don't have that kind of phone but two things come to mind... do you have an SD card in your phone? If it's not seated properly it can cause buzzing noises. My daughter had a similar problem. Also, once I had an app (can't remember what it was) and several times during the day that I downloaded it, it would make a strange ring tone. I uninstalled the app, then reinstalled, and it never happened again.