A number that rings while the app is open can still miss a call once the phone is locked in your pocket. Before you print it on a business card or give it to a landlord, spend an hour checking that it does the jobs you need. You only need your phone, a second phone and a friend or colleague in the US who agrees to help.
Start with your must-haves
Write down the few things that would make the number useless to you if they failed. For example:
- US clients must reach me when my phone is locked.
- I must call US and Canadian numbers without surprise costs.
- Callers must be able to leave voicemail when I cannot answer.
- Codes from the apps I use must arrive.
The TripoSIM US number receives texts but cannot send them, and it cannot call 911 or other emergency services. If either is on your must-have list, it is not the right main line for you, however well the other checks go.
The ten checks
| Check | How to run it | It passes when |
|---|---|---|
| 1. Your number | Note your +1 number in the Phone tab and call it from another phone | It rings on your phone |
| 2. A call in | Ask a US contact to call you as they normally would | You answer and hear each other clearly |
| 3. A call to the US | Call a US contact who agreed to help | The call connects and sounds clear on both sides |
| 4. A call to Canada | Call a Canadian number | The call connects and the minutes are counted |
| 5. Screen locked | Lock the phone, wait two minutes, then have someone call | You see and hear the call and can answer it |
| 6. Network switch | Turn off Wi-Fi so the phone uses mobile data, then call again | It still rings and the call holds |
| 7. Voicemail | Miss a call on purpose | The message shows in the app and plays |
| 8. A text | Ask a US or Canadian contact to text you | The text appears in the app |
| 9. Minutes | Check the minutes used after your test calls | The count matches the rule below |
| 10. Backup | Check your renewal date, what happens if you stop paying, and a second way to reach you | You know how you keep the number and how people reach you if a call fails |
On minutes: Each outgoing call is rounded up to the next full minute; unanswered calls are free. A 61-second test call therefore uses two minutes.
Run it on the phone you will actually use
A desktop browser tells you nothing about how a phone behaves once it locks or saves battery. On iPhone, add the TripoSIM web app to your Home Screen, then allow notifications and the microphone. On Android, install the TripoSIM app, allow the same, and stop Android from optimising its battery use.
For every check, note the phone model, its software version, whether you were on Wi-Fi or mobile data, the country you were in and the time. If a check fails, the guide to making your number ring reliably covers notifications, Focus modes, Low Power Mode and Android battery settings.
How many times to repeat each check
A single pass only shows that something worked once. Repeat each important incoming-call check five times in the same conditions, then five more on your other network. Five is a practical check, not a reliability figure: if 18 of 20 calls rang, write “18 of 20”, not “90% reliable”.
| Phone state | What to record |
|---|---|
| App open | Did it ring, and could you answer? |
| Screen locked | Did you see and hear the call, and how many seconds did it take? |
| Another app in front | Did the call notice appear and bring you to the call? |
| Mobile data only | Did it ring, and did the call hold? |
| Low Power Mode or battery saver on | Was the call late, silent or missed? |
| No internet at all | Did the caller reach voicemail? (With no connection the phone cannot ring.) |
Score each check, then decide
Give every check one of four results:
| Result | Meaning |
|---|---|
| Pass | It worked on your phone and network, every time you tried |
| Fail | It did not meet the “passes when” line |
| Not tested | You have no result yet, so it does not count as a pass |
| Not offered | The service does not include it |
Then decide by your must-haves, not by an average. A number that passes nine checks but misses calls when locked is the wrong number if locked-screen calls are what you need.
- Ready: every must-have passed every time.
- Ready with a backup: every must-have is offered, but you have not tested enough, so keep email or a contact form alongside it.
- Not right for this job: a must-have failed or is not offered.
- Test more first: you have not tested your must-haves yet.
Check the cost against your calls
Count the calls you make in a usual month. 25 calls of 10 minutes is 250 minutes, inside the 300 outgoing minutes included each month. 50 calls of 10 minutes is 500 minutes, so you would add two top-ups of 100 minutes at $5 each. The cost calculator and the 300-minute guide work this out for you.
Download the blank test log
Download the test log (CSV). It opens in Excel, Numbers or Google Sheets, with one row for each of the ten checks and columns for the phone, network, result and notes. It has no results filled in.
If you share your results, leave out full phone numbers, verification codes, voicemail recordings and anything that identifies the people who helped.
What this page is, and is not
This is a method for testing your own number. It is not a report of tests we ran on every phone and country. TripoSIM’s own tests from October 3 to 18, 2026 covered verification codes from 22 apps; you can see them in the verification research. The call checks above are for you to run where you live, on the phone you use.