If you are wishing to stick with AT&T, I have created a search results page of all the available AT&T plans with a search filter set at 4 GB of data and higher. From these results, you will be able to compare data inclusions to choose your best option.
Click here to Compare AT&T 4GB Data (and higher) Plans
Now, if you are wishing to switch carriers, here is a search results page of all the compatible carrier options and prices for 5 GB plans on your devices.
Click here to Compare all BYO Options
The prices for each plan upfront and monthly are listed under each carrier’s link. All of these carriers will be compatible with your devices making your switch super easy!
FYI: iPhone 6 Apple devices and newer generation iPhones are compatible across the board. Whether GSM or CDMA technology, they are compatible with most every carrier. This means you could take your devices to just about any carrier.