iOS Tip 162 - Measure Your Signal Strength

If you're measuring your cellphone signal by the little dots in the top-left hand of your iPhone's display, then you're really missing out on a cool feature: using the built-in Field Test Mode feature.

You access this feature from your Phone app, but before you do that you need to do a couple of things:
• Turn off Wi-Fi (Settings > WiFi)
• Turn off LTE, because these readings can be different from standard cellphone signals (Settings > Cellular > Enable LTE)
Now you've got that out of the way, go to your Phone app, switch to the keypad and dial the following:
Now press Call and you'll activate Field Test Mode.

To exit, just press the Home button.

If you want to replace the signal strength dots with a decibel value, press and hold down the power button until the Slide to power off message appears. Then release the power button and then press and hold the Home button for around five to ten seconds until the Field Test Mode screen disappears.
A high signal score is around -50 decibels, while a weak signal will be around -115 decibels, so basically the closer to zero the number is, the better your reception.

iOS Tip 122 - Avoid Unwanted Cellular Useage

Turn Off iOS 9 Wi-Fi Assist to Avoid Unwanted Cellular Usage

Hidden deep in iOS 9 is a setting that Apple intended to improve your iPhone experience. Called Wi-Fi Assist, it enables iOS 9 to use cellular data automatically when Wi-Fi connectivity is poor. That’s a nice idea, but it also means that your iPhone (or cellular iPad) may use lots of expensive cellular data when you’re not expecting it to. If you worry about cellular overage charges, turn this feature off in Settings > Cellular > Wi-Fi Assist (it’s near the bottom).

iOS Tip 121 - Enable Wi-Fi Calling

Enable Wi-Fi Calling to Improve Call Quality

If you use AT&T, T-Mobile, or Sprint in the United States with an iPhone 6 or later, you can turn on a feature in iOS 9 that enables your iPhone to send calls over a Wi-Fi network (and thus the Internet) rather than relying on spotty cellular coverage. It’s especially helpful in thick-walled buildings that block cellular signals. To enable it, go to Settings > Phone > Wi-Fi Calling and run through a few screens that explain the service. You'll be asked to provide an address, so your carrier can associate that address with your call if you make an emergency 911 call over Wi-Fi. (When you call 911 over a cellular connection, the 911 operator will automatically see your actual location; if you turn on Wi-Fi Calling and Wi-Fi is used for your emergency call because cellular won’t work, the operator will receive the address that you provided, regardless of your location.)

iOS Tip 90 - Avoid Data Overages When Travelling

How to Avoid Data Overage Charges When Traveling outside the US

Disable any apps that you don’t plan to use in Settings > Cellular. It’s tempting to disable only those that have used data in the past period, but it can be hard to predict when an app willdecide to retrieve a large amount of data. Be especially cautious about apps like Music, Photos, Podcasts, Dropbox, Skype, Google Hangouts, and Spotify that might want to stream media, sync data, or provide real-time high-bandwidth communication.

* To prevent email and calendar data from outside arriving on youriPhone unbidden, go to Settings > Mail, Contacts, Calendars > FetchNew Data, turn off Push, and select Manually in the Fetch section. The data will update when you launch the associated app.

* Also, in Settings > iTunes & App Store, turn off Use Cellular Data. To be safe, I’d also recommend disabling automatic downloads. Thatway your iPhone won’t automatically get downloads for purchases made by someone else in your Family Sharing circle, or those made on a device you left at home while you’re travelling.