- A
The device's data roaming is turned off.
Why wrong: Data roaming affects data while traveling, not local voice calls.
- B
The device's preferred network type is set to 'LTE only' and VoLTE is disabled.
On some networks, 'LTE only' without VoLTE prevents voice calls because the network doesn't fall back to 3G/2G for voice.
- C
The device's Bluetooth is enabled.
Why wrong: Bluetooth does not affect cellular voice call capability.
- D
The device's airplane mode is turned on.
Why wrong: Airplane mode disables all cellular functions, including texts, so the user wouldn't be able to send texts.
Question 994 of 1,020
Smartphone Can Send Texts But Not Make Calls: VoLTE Misconfiguration
This 220-1201 practice question tests your understanding of mobile device network connectivity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is troubleshooting a smartphone that can send and receive text messages but cannot make or receive phone calls. The device shows full signal bars. Which network setting is most likely misconfigured?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Quick Answer
The answer is a misconfigured preferred network type set to 'LTE only' with VoLTE disabled. This is correct because text messages can travel over the LTE data channel using IMS signaling, even without VoLTE, but voice calls require either a circuit-switched fallback or a dedicated Voice over LTE connection. When VoLTE is disabled and the network is locked to LTE, the phone has no pathway to place or receive calls, despite showing full signal bars. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your understanding of how modern carriers handle voice versus data traffic, often appearing as a troubleshooting question where the user can send texts but not make calls. A common trap is assuming signal strength alone guarantees call capability, but the real issue is the missing VoLTE provisioning. Remember the mnemonic: "Texts ride data, calls need a gate—VoLTE must be the state."
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The device's preferred network type is set to 'LTE only' and VoLTE is disabled.
When a smartphone shows full signal bars but cannot make or receive voice calls while SMS works, the most likely cause is that the device is set to 'LTE only' as its preferred network type and VoLTE (Voice over LTE) is disabled. SMS can be carried over LTE via IMS (IP Multimedia Subsystem) or fallback to circuit-switched networks, but voice calls require either VoLTE or a circuit-switched fallback (CSFB) to 2G/3G. With 'LTE only' selected and VoLTE off, the device cannot initiate or accept voice calls because it lacks a circuit-switched connection and has no fallback path.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The device's data roaming is turned off.
Why it's wrong here
Data roaming affects data while traveling, not local voice calls.
- ✓
The device's preferred network type is set to 'LTE only' and VoLTE is disabled.
Why this is correct
On some networks, 'LTE only' without VoLTE prevents voice calls because the network doesn't fall back to 3G/2G for voice.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The device's Bluetooth is enabled.
Why it's wrong here
Bluetooth does not affect cellular voice call capability.
- ✗
The device's airplane mode is turned on.
Why it's wrong here
Airplane mode disables all cellular functions, including texts, so the user wouldn't be able to send texts.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The 220-1201 exam often tests the misconception that full signal bars guarantee voice call capability, but the trap here is that signal bars only indicate LTE signal strength, not the availability of a voice-capable network layer (circuit-switched or IMS).
Detailed technical explanation
How to think about this question
VoLTE uses the IMS core to transport voice as IP packets over the LTE data channel, requiring the device to register with the IMS network. If the preferred network type is locked to 'LTE only' and VoLTE is disabled, the device will not attempt CSFB to 2G/3G (which would be unavailable anyway) and will not register for IMS, leaving voice calls unserviceable. In real-world scenarios, carriers often require VoLTE to be enabled for voice on LTE-only networks, and some devices hide the VoLTE toggle when the carrier does not support it, leading to confusion when troubleshooting.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Mobile Device Network Connectivity — study guide chapter
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Mobile Device Network Connectivity — This question tests Mobile Device Network Connectivity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The device's preferred network type is set to 'LTE only' and VoLTE is disabled. — When a smartphone shows full signal bars but cannot make or receive voice calls while SMS works, the most likely cause is that the device is set to 'LTE only' as its preferred network type and VoLTE (Voice over LTE) is disabled. SMS can be carried over LTE via IMS (IP Multimedia Subsystem) or fallback to circuit-switched networks, but voice calls require either VoLTE or a circuit-switched fallback (CSFB) to 2G/3G. With 'LTE only' selected and VoLTE off, the device cannot initiate or accept voice calls because it lacks a circuit-switched connection and has no fallback path.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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