Why standardise Telephone numbers in Salesforce?
You may have noticed that contact numbers on websites are sometimes listed twice, once with 'National/Local' and another as 'International'.
Here's an example:
Local - 202-555-0138
International - (001)-202-555-0138
The reason for listing the number twice is because when you are calling within in the same country you can dial a shorter number.
However, if you need to call in from one country to another, you will need to add a country code/prefix to make sure the telephony systems understand you are calling internationally.
This works the other way around too.
If one of your customers calls you from outside your own country their number is going to 'present' on your handset with the country code at the front of it, whereas if the call is domestic it will not.
It is useful to have all of your numbers in Salesforce set up in one standard format to ensure your customers get recognised each time they call in, (regardless of whether they are calling domestically or internationally).
Luckily, a few years ago the International Telecommunication Union defined a common standard for telephone numbers which would work nationally and internationally. This standard allows someone to dial a number from one county to the other without issue, from anywhere in the world.
They called this standard E.164 (catchy, eh?).
A properly formatted E.164 number would show like this:
To learn more about the full specification of E.164 visit this page: https://en.wikipedia.org/wiki/E.164
Time to review your numbers?
It may be worth checking through your customer telephone numbers in Salesforce to see if they are in a recognised format and consistent. If not, then you'll either need to tidy them manually or consider getting an app like RingsTrue to do it for you.