Beware the fact that on many phones 4G means just 3G++.
My Galaxy S4 shows 4G in HSDPA+ zone. It turns to H+ when idle and 4G when active data transmission is taking place. BB Bold 9900 also shows 4G for what is actually a 3G++ (HSDPA+).
4G LTE would show a "4G LTE" icon instead of just simple "4G".
See comments here
4G icon vs. LTE icon: What's the difference? - Windows Phone Central Forums
So even if your phone shows 4G you may not necessarily be using LTE.
My Galaxy S4 shows 4G in HSDPA+ zone. It turns to H+ when idle and 4G when active data transmission is taking place. BB Bold 9900 also shows 4G for what is actually a 3G++ (HSDPA+).
4G LTE would show a "4G LTE" icon instead of just simple "4G".
See comments here
4G icon vs. LTE icon: What's the difference? - Windows Phone Central Forums
So even if your phone shows 4G you may not necessarily be using LTE.