On Jellybean, I can be in a building, unable to get LTE, but have strong 3G/HSPA+ connection and it works great.
Ever since upgrading to Kitkat though, while LTE continues to work great, if not faster in my speed tests, when on 3G/HSPA+, after a short while, the data connection seems to freeze. I'll see it drop from H+ to 3G in the menu bar, and just merely a flashing up arrow, and nothing else. It never seems to fix itself, and I just have to put the device to sleep by tapping the power button. Within a minute it regains a good data connection again for maybe another 2 minutes. This is constant.
I'm at a loss, it's a new phone and only had it for 2 months. It's not rooted or anything like that, just unlocked by the distributor, and on T-Mobile (if that matters).
It's getting annoying because it makes using my data connection completely unusable. Samsung techs were actually quite helpless, they wanted me to send in my phone, but it seems to be software related because it worked fine on Jelly bean. It literally happened RIGHT away after the kitkat upgrade.