The answer is an incorrect or missing SMS message center number (SMSC). This is the most likely cause because the SMSC acts as the routing hub for all text messages; without the correct number stored on the SIM or device, the phone cannot send or receive SMS, yet voice calls and mobile data remain unaffected since they operate over separate signaling paths—circuit-switched fallback for calls and packet-switched networks for data. On the CompTIA A+ Core 2 220-1202 exam, this scenario tests your understanding of how different mobile services use distinct network layers, and a common trap is to blame the SIM card itself or the network signal when the real issue is a misconfigured SMSC, especially after a SIM swap. Remember the memory tip: “Calls and data are fine, but texts are blind—check the SMSC number you need to find.”
220-1102 Mobile OS and App Troubleshooting Practice Question
This 220-1202 practice question tests your understanding of mobile os and app troubleshooting. 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 an Android phone that cannot send or receive SMS messages, but can make and receive calls and use mobile data. The phone is on a corporate plan with a new SIM card. What is the most likely cause?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The SMS message center number is incorrect or missing.
The SMS message center number (SMSC) is a required parameter stored on the SIM card or phone that tells the device where to route outgoing SMS messages for delivery. If this number is incorrect or missing, the phone cannot send or receive SMS, but voice calls and mobile data remain unaffected because they use separate signaling paths (CSFB for calls and packet-switched data for mobile data). A new SIM card may have a misconfigured or missing SMSC, which is the most likely cause given the symptom pattern.
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 phone's IMEI is blacklisted.
Why it's wrong here
A blacklisted IMEI would typically block all network services, not just SMS.
✓
The SMS message center number is incorrect or missing.
Why this is correct
The SMSC is required for SMS routing; if it's wrong, SMS will fail while other services work.
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 mobile data APN settings are incorrect.
Why it's wrong here
APN settings affect data and MMS, not basic SMS, which uses the control channel.
✗
The phone is in airplane mode.
Why it's wrong here
Airplane mode would disable all cellular services, including calls and data, not just SMS.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between services that use the control plane (SMS, voice) versus the data plane (mobile data), leading candidates to incorrectly blame APN settings (Option C) when the issue is actually a missing SMSC number.
Detailed technical explanation
How to think about this question
The SMSC number is typically stored in the SIM card's EF (Elementary File) under 6F42 (SMSP) and is queried by the phone during SMS submission using the GSM 03.40 protocol. If the SMSC is missing, the phone may still receive SMS via the network's SMS center if the network pushes them, but sending will fail because the phone cannot construct the proper TPDU (Transport Protocol Data Unit) without a destination SMSC address. In some Android devices, the SMSC can be viewed or set via the engineering menu (e.g., *#*#4636#*#*), but corporate-managed devices may lock this setting.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1202 question in full detail.
Mobile OS and App Troubleshooting — This question tests Mobile OS and App Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The SMS message center number is incorrect or missing. — The SMS message center number (SMSC) is a required parameter stored on the SIM card or phone that tells the device where to route outgoing SMS messages for delivery. If this number is incorrect or missing, the phone cannot send or receive SMS, but voice calls and mobile data remain unaffected because they use separate signaling paths (CSFB for calls and packet-switched data for mobile data). A new SIM card may have a misconfigured or missing SMSC, which is the most likely cause given the symptom pattern.
What should I do if I get this 220-1202 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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