Make sure that you are NOT dialing the + (plus sign) as listed in the dialing instructions.
Make sure that you leave off the starting "0" in some cases. For example, calling someone in London, UK domestically would be dialed as (020) Local Number, but but if you're calling from another country, you would drop the initial 0 from the City/Area Code and dial 44 + 20 + Local Number
If you have verified that the numbers you are dialing are correct, consider the following:
Verify that your land line or mobile phone allows for International calls.
Verify that the number you are calling accepts international calls. Some numbers block these calls, such as toll free numbers.
If you are using a VoIP service, you may not have to include the Exit Code when calling internationally.
When calling mobile numbers outside of the United States to other countries, an Area/City Code is not always required. Check our mobile codes search to get specific dialing codes for calling a mobile phone internationally.