Usage needs - since we live in a complicated driving area, we use the GPS mapping feature often. We use the Web occasionally, once or twice a day. We never stream music or videos unless we're on wireless. We are nearly always covered with wireless access (home/work/church, etc) except when we're in the car or when I'm out on a long bike ride. I sometimes will use a workout tracking device on the iPhone to remember my route/time while riding.
If you want to use your iPhone as a GPS unit, buy
Sygic's offline GPS maps instead. That'll nip your data usage needs right in the bud. Most all that other stuff should be able to work offline as well, except for the web browsing, but that's more of a self-discipline thing. Speaking of self-discipline, the only real way you'll be able to save any real money on these devices is to ditch the heavy data habit.
Do you have a home phone? How much of that calling is done from home? If you're making a lot of calls from home and don't have one, bring back the home phone with a VoIP provider as has already been mentioned.
Guessing a fair bit of that text messaging is back and forth between the two of you and maybe one or two other people? Use an SMS text replacement that uses data instead.
XMS or
Kik would be simple options that would use data instead of SMS and handle most of those MMS needs if the people sending/receiving MMS messages are the same people you do your bulk of texting to. Alternately, if you'd rather go oldskool, bust out the Google Talk chat accounts and use them with
Talkonaut or the official Google client. Unfortunately, those require data services to be left on with the iPhone, and the iPhone is a hungry-hungry hippo with background data usage. You're starting to see how drastic a move it takes sometimes to get the iPhone to behave like a frugal phone device now given you don't have to jump through hoops to balance as much even with Android as Apple's idea of network data control is a giant ON/OFF switch, whereas like the Android platform for example has a far more granular control over what can and cannot go online. Symbian and Java devices just won't go online except for the applications you specifically want online to begin with, like email and those SMS replacements.
There's ways around this with mobile hotspots and just carrying those instead of turning on data with the phone. MMM uses the FreedomPop hotspot as do a few others around here due to a free usage tier, and there's a plethora of other cheap Sprint data options as well from
Virgin Mobile and
TruConnect's Internet on the Go, but it does complicate the setup a bit. It will be needed, however, if you want to stick with an AT&T MVNO and don't want to pay upwards of $45+ a month per phone. If you were open to going T-Mobile as it appears there's pretty good coverage by them in the region, that gives you the option to do $35 a month with GoSmart per handset if you'd rather just limit your data access speeds to keep it one device, but at that point you might as well go with a T-Mobile postpaid option, which may be cheaper than what you're paying now, but still criminally priced for what you're actually using as I suspect you've long ago realized.
As I told someone else in PM just yesterday:
It's a little less convenient, but even going with Virgin's $35 plan plus the Airvoice $10 plan... is a single device convenience with ~2GB of average speedier broadband access really worth an extra $85 a month? Or is single provider service with 3G data access speed worth the extra $95 a month?
...
As you can see, with some major data discipline and the introduction of a third phone line back in the house, you could slice your average phone bill down from $170 a month to under $30. Even if you refuse to discipline your data usage, with a few convenience hacks in its usage, you could still drop your monthly costs down to between $70-100 a month which still isn't anything to sneeze at. Ultimately though, we're talking about mostly superfluous services, and the parts of it you deem necessary should be separated from the desires brought on through wussypants hedonic adaptation. Once you see how much that lazy adaptation part's really costing you in relation to what you actually need, you'll be able to better quantify if the added cost is really worth it.
The numbers don't necessarily entirely apply to you, but they're struggling to save money with two iPhones as well and the advice should still ring true in this situation as you too have the
potential to hit that $30/month for everything sweet spot that they do... low minutes, light/moderate texting, and a buttload of data. It's the data that's going to eat you alive in costs, and it's the price of that data convenience you should be weighing in relation to that $30/month price point versus higher costs just to keep your iPhones and their constant hunger for data flowing. Humorously enough, with those usage numbers, Ting would be a prime candidate for you to go to as your average monthly bill would be $48+tax without you changing a single thing in usage habits... except, well... CDMA provider and no bringing even Sprint CDMA iPhones for activation. This would mean tossing the iPhones and re-investing in all new hardware and being locked into Ting/Sprint MVNOs that allow BYOD for the most part. The iPhones themselves are literally your biggest stumbling block on roping in these costs. If you're willing to do that sort of handset change, you're far better served staying GSM if you're looking to do the cost saving MVNO route.
As for your usage numbers specifically and as mentioned before, if T-Mobile coverage isn't objectionable to you and you could really rope in that data use to "only as needed" and kept to a bare minimum,
Platinumtel might be a better option (at least for your wife), with or without using VoIP at home. It's an extra penny a minute, but SMS rates are the same, data's 23¢ a MB cheaper, and you won't have to layer multiple $10/month refills a month to ensure you have enough credits to call without you both having to hit that $30+ a month range. If you can offload a bulk of those minutes used on your phone to a VoIP provider at home, you'd be absolutely laughing on your own end and could do likewise, otherwise you're looking at something like Airvoice or GoSmart's $30+/month unlimited talk and text plans given you're pushing usage numbers that get close to break even on per minute costs with the unlimited packages.