Incorrect number formatting is the most common reason calls fail.
This issue often appears after traveling. Numbers saved in local format work inside one country, but fail internationally unless they are updated with the full country code.
Correct international format
Use this format for all international and landline calls:
+ or 00 + Country Code + Area/City Code + Phone Number
Example
Local: 07123456789
International: +44 7123456789
Important rules
Always include the country code
Remove any leading 0
Do not use spaces, dashes, or symbols
Save contacts exactly in this format
📌 For + vs 00 differences, see When Should I Use + or 00 When Dialing?