After installing the FastCall Click-to-Call application from the Salesforce AppExchange and connecting Twilio, you have one more step if you are dialing outside the US or Canada. Log into Twilio and add international dialing.
Twilio expects a country code when dialing outside the USA or Canada. A country code can be set as a default for the org, or for each user under User Settings. When a default country code is set for the org, FastCall considers this the “home country.” If a phone number in the home country has a leading “0” FastCall will remove the number before dialing. Only in the home country. Outside of your home country code you will need to verify the correct format in the Salesforce phone number field as described below.
For example if your home country is the UK, FastCall will strip a leading “0” before a number. If calling France from the UK you must remove the leading 0 from the phone number field.
See the install instructions for more details.