Can T-Mobile transfer all my data when I upgrade from the iPhone 5s to the iPhone 6 Plus?

I'm upgrading my phone soon and I want to know if T-Mobile can transfer all my music, texts, phone numbers, apps, etc. To my the new device.

They should be able to, but you can do it yourself. Just back everything up to iTunes on your computer, and when you get the new computer setup, just restore to the new phone.

Recently, i found another very useful iphone data manger tool, named AnyMP4 iPhone Transfer Pro, it helps me a lot, it makes manage iphone data easily. For example, it can freely transfer files like videos, photos, images, etc. Between iphone and pc. It can also backup sms and contacts on my computer to avoid lost the important contacts.