I'm using a Lumia 435 (unlocked T-Mobile phone) with Ting GSM, and it works great for voice and texting. Its WIFI also works fine. However, oddly, the cellular data seems to work for some things and not others. For example, maps, traffic, and the weather app all work fine on data alone. But data will not update my calendar (which does update when I get in Wifi range), and I can't seem to get group texts. Any ideas?
Microsoft Lumia 435