Why Your 4G Watch Can't Make Calls: The Hidden VoLTE Trap

In the sprawling digital marketplace, a new category of device promises the ultimate technological freedom: the “phone-on-your-wrist.” These gadgets, often from unfamiliar brands, boast specification sheets that seem too good to be true: full Android operating systems, massive 4GB+64GB storage, dual cameras, and the all-important 4G/LTE SIM card slot.

They promise a world where you can leave your bulky smartphone behind. A world where you can run, hike, or simply go to the store, yet remain fully connected.

A device like the Rainbuvvy 4G Smart Watch is a perfect example. On paper, it’s a powerhouse. In reality, it holds a 1.7-star rating. Its user reviews are a chorus of frustration: “Does not support voice over lte,” “the claim it will replace your phone is totally false,” “worthless,” “Does not connect to cellular system.”

This isn’t just a case of one bad product. It’s a case study in a critical, invisible technological gap that has rendered countless 4G devices in North America useless. This is the story of VoLTE.

The “3G Sunset” and the Lost Voice

To understand this catastrophic failure, we must look at the infrastructure we’ve left behind. For decades, mobile networks were simple. 2G (GSM) networks handled our voice calls. 3G networks gave us our first taste of mobile data. In this world, voice and data were separate.

But the demand for high-speed data—for streaming video, social media, and a connected world—exploded. To build the superhighways for 4G and 5G, carriers needed to reclaim the “spectrum” (the radio frequencies) used by older, slower technologies. This led to the “3G Sunset.”

In the United States, all major carriers, including T-Mobile, AT&T, and Verizon, have completely shut down their 3G networks. This event was a silent death knell for older devices, but it also created a profound engineering problem: If the 4G network is built for data, how do you make a voice call?

VoLTE: The Non-Negotiable Protocol

The 4G LTE network was engineered as a high-speed “all-data” network. It was not originally designed to handle the traditional “circuit-switched” voice calls of the 2G/3G era.

The solution is VoLTE (Voice over Long-Term Evolution).

Think of the 4G network as a massive, multi-lane highway built for internet traffic. VoLTE is a special, prioritized “express lane” created exclusively for voice. When you make a call on a VoLTE-compatible phone, your voice is converted into data packets. These packets are given a “VIP” status, allowing them to bypass all the regular data traffic (like streaming music or loading a webpage). This ensures they are delivered instantly and in the correct order, which is what provides the clear “HD Voice” quality we now take for granted.

In the post-3G-Sunset United States, VoLTE is not an optional feature. It is the only way for a device to make or receive a voice call over the cellular network.

The Anatomy of a 1.7-Star Failure

This brings us back to the Rainbuvvy 4G watch and its angry customers. The product’s specifications are not technically a lie. It does have a 4G radio. It can connect to 4G LTE bands. You can probably use its 4GB of RAM to browse the internet, download apps from the Google Store, or use GPS mapping.

But its engineers, targeting a global market, missed the single most critical protocol for U.S. carriers: It does not support VoLTE.

Without VoLTE, the watch is like a person at a party who can see and hear everyone but is incapable of speech. It connects to the 4G network, but when it tries to make a voice call, the network has no idea what to do with it. There is no 3G network to “fall back” on. The call simply fails.

This is the “ghost in the machine” that explains every 1-star review. The core promise—“it can answer and make calls independently… you can replace your cell phone”—is rendered completely false in the U.S. market.

The Compounding Problems: Specs vs. Reality

The VoLTE issue is the fatal flaw, but it points to a larger problem with devices that promise everything for a low price. The impressive specs often hide a mountain of real-world compromises.

• The “Full Android” Trap: The watch runs Android 9.1, an operating system designed for smartphones. This is incredibly inefficient on a tiny watch processor, even with a “dual system” chip. The result, as one user notes, is a battery life of only 8 hours, despite a massive (for a watch) 1050mAh battery. The “Bracelet mode use time: 5-7 days” listed is a marketing fantasy for its actual smart features.
• The Dual Camera Gimmick: The 5.0MP dual cameras are a “spec-sheet” feature designed to look impressive. In reality, they are a significant drain on battery and, on a device this small, offer questionable utility.
• The “Waterproof” Mirage: The IP67 rating means it’s rated for dust and brief immersion in 1 meter of still water. It is not waterproof for swimming or even showering, where water pressure can easily bypass the seals.
• The Service Black Hole: When a “charger burned out,” one user found “no replacement everywhere” and “No response from mfg.” This is the risk of purchasing “pump and dump items” from transient, no-name brands.

Before you buy any 4G smartwatch that promises to replace your phone, especially from a non-major brand, you must ask one question that supersedes all others: “Does this device explicitly support VoLTE on my specific carrier?”

If the seller cannot provide a clear, affirmative answer, then all other features—the 64GB of storage, the dual cameras, the full Android OS—are irrelevant. You are not buying a “phone-on-your-wrist”; you are buying a tiny, 4G-connected data tablet that, in the modern U.S., is fundamentally mute.