4G non-VoLTE devices use 4G for data, offering fast internet speeds, but cannot make calls over the 4G network because they lack VoLTE (Voice over LTE) support.

Here's a break down:

• 4G Data: These devices provide quick internet access through 4G networks, ideal for browsing, streaming, and downloading.
• No 4G calls: Without VoLTE, they can't make voice calls over the 4G network, missing out on the improved call quality VoLTE offers.
• Relies on 3G for calls: To make or receive calls, these devices switch to older 3G networks, which are slower and being phased out.
• Impact of 3G shutdown: As 3G is phased out, users with 4G non-VoLTE devices will still be able to use their device for data, but won't be able to make voice calls.

In summary, 4G non-VoLTE devices have fast 4G internet capabilities, but do not have modern voice call technology, and won't be suitable to use as a phone after 3G is switched off.