I really screwed up last week and purchased a GSM phone from Ebay. Big, big mistake. The phone is a new unlocked Samsung Galaxy S III GT-I9300 (Model # SGH-T999) with Android Version 4.1.1 ”Jelly Bean”. When it arrived, the phone had "T-Mobile" written on the back and all the apps seem to be from T-Mobile. It also states that the carrier is T-Mobile. The seller of this phone never reviled this information. However, it is a very nice phone. Here is my problem. I am using H20 Mobile prepaid service which exclusively uses AT&T Mobile. I want to use this phone for AT&T service because they have the best reception in my local area. The T-Mobile reception is terrible here. While driving, sometimes the phone wants to connect to T-Mobile towers and indicates the service is not available. Also, the internet connection tries to connect through T-Mobile while on the road. The message says I don’t have an account. My question: is there software available for download that I can reprogram this phone and use it with AT&T service?? I want to completely wipe T-Mobile off this phone. I am not sure what the next step should be but I have downloaded the latest ROM software "51c37773dec1b" V 13 called ”Jelly Bean”. I haven't installed it on my phone yet. Is it possible that this software upgrade might resolve the problem of this phone trying to connect to T Mobile towers???
An OS update won't improve your connection quality unless it also contains updated radio firmware (which it might). It's worth a try and won't hurt anything. If the phone doesn't work with your SIM card and isn't unlocked so that it will work with your SIM card, then you should dispute the transaction with eBay and return the phone. If it does work with your SIM card (you can make calls and access data) but it prefers T-Mobile over your carrier, then it's harder to say how to deal with the problem. If your carrier prefers to use AT&T towers, then the phone should follow that. But H2O might be small enough that the phone doesn't have info on how to work best with your carrier and SIM card.
-------------------- Lisa Gade Editor in Chief, MobileTechReview