You are not alone on issues related to weak signals. It happens to us all regardless of the carrier in the US.
I have an iPhone4, legally unlocked with replaceable SIM that I use here In Australia, the US and Europe. I simply replace the SIM to phone accounts in other countries. Do have issues at home here in Australia from time to time, but many more problems in the US than any other country.
When the signal is weak, ususally 1 bar the phone does not have enough power to stay connected. It will attempt to receive and send, but is trying to process so much that the signal cannot cope.
If any employee from Sprint, ATT or any other carrier attempts to tell you it is you and not their system they are out right lying. Just as they lied when they told you that the iPhone was 4G. Some try to get around the issue by saying 3GLite, but that really does not apply either because of the mobiles frequency range.
In fact the Australian government fined Apple AUD$2.25 million + $330,000 in costs for advertising that the new iPad was 4G and LTE, which it is not. There is currently another legal challenge over the iPhone4S.
If you have anything in writing from Sprint that says 4G then you need to contact your states attorney general. At least file a complaint with both Sprint and the FCC. If they tell you it is 4G then they either are lying or they do not have a clue to the mobile.
When the signal is weak the phone keeps attempting to send anything that you have sent. Sometimes that means multiple sends if the signal keeps dropping to low and it has to try all over again.
One way around the problem is by using an internet or data based app like Viber or WhatsApp. Both are voice, text and data Apps that will use Wi-Fi first then 3G if Wi-Fi is not available. Because they use the data side of your mobiles plan it does not take as much power or size to receive or send. Plus, because they are primarily Wi-Fi then data bases they do not use as much time or text units. You can find them online or through the Apple App Store.
Iv used Viber for years because I can use it overseas or talk, video, text or msg internationally without use of any mobile plan time.
Rember to that in the states you have I think 72 days to return a mobile to the carrier without any charges.
I use ATT in the states and when I am at home here I get almost no signal ... I depend 99% on Viber or WhatsApp to even talk.
It also resends messages without me knowing.
I will have perfect signal and send a message just fine. Hours later someone will text me and tell me I keep sending the same message over and over. My phone won't even tell me that it's doing it. I have unlimited data, yet everywhere I am, I have extremely slow 3G. The internet will barely even load a page. It seems to get slower and slower. Sometimes it will just say "no internet connection" when I have full service and 3G. The reason I switched from AT&T with an iPhone 3GS to Sprint with an iPhone 4S, is because they told me the service would be better and also for the new 4G. My internet was faster with AT&T 3G internet service than it is with Sprint. My friend kept her iPhone on AT&T and has 4G service. It works excellent everywhere. I don't have in writing that they told me 4G would be on my iPhone, but I told the guy that was one of the main reasons I was getting this new iPhone that supports 4G, and he said it should be a month before they have it in my area. I walked into the Sprint store last week, and asked them why I don't have 4G and they pretty much all tried to argue with me and said NO phone company has a 4G iPhone. AT&T does for sure! They also told me the reason my phone was re-sending messages constantly was because my time zone on my phone wasn't set on Chicago, but it is. Many times every month, my phone quits receiving calls, making calls, receiving messages, or sending them. I call Sprint customer service and they tell me it's a tower problem. Really, a tower problem that many times even in different areas that I'm in. I don't think that's the problem. One time it quit working for a good 24 hours. I've tried everything I could do with this phone to make it work. Like them giving me a ticket and doing tests or whatever on my phone. They always tell me it's a tower problem. I've talked to friends about this that have iPhones on Sprint, and they claim that their iPhones keep resending things. Also, it gets text messages in pieces which can get annoying.
That all sounds a bit fishy and I'd take it back to Sprint. If you have past the return time limit then ask for a manager or a tech advisor, not one of the counter employees. Or if you live near an Apple store go online and book time with an Apple Genius.
Without seeling the mobile it is hard to say. Has the mobile been updated with all current and past updates? Has every App been updated?
Are you a Mac user or do you have iCloud to back up your info on the mobile if you go back to factory settings?
I do not have an iPhone4S so not up on any problems with that series. Maybe someone else reading this can help more.
As for 4G ... there are mobiles that have 4G or LTE technology and they were nuts to tell you that.
Time zone settings, language, etc ... have absolutely nothing to do with whether the mobile can or cannot send or receive. I use my iPhone4 all over the world and have for years. Though you do have to wonder why you cannot get a signal sitting at home in your house in the US when I can get 5 bars sitting on safari in the middle of the Richtersvelf National Park in Namibia
I walked into the Sprint store last week, and asked them why I don't have 4G and they pretty much all tried to argue with me and said NO phone company has a 4G iPhone. AT&T does for sure!
No, not really. The 4G standard is an evolving one. Most of the major carriers in the U.S. are moving to 4G LTE as their next generation, faster speed network.The current model iPhone doesn't work on the 4G LTE network. AT&T calls their HSPA+ network "4G". That's more marketing hype than anything. It isn't as fast as 4G LTE, though. So, no, the iPhone isn't really considered a "4G phone".
Ever since Sprint released the iPhone, there have been numerous articles about how much slower the data speeds are than on AT&T or Verizon. An internet search will turn up lots of hits, including ones to the Sprint Community Forums.
This is what I'm going through with Sprint right now...
Above is my Apple post rather than my Sprint post. Sprint has been rejecting and editing portions of my posts (keep in mind that I'm not using profanity, just stating facts).