Small problem. Can't seem to figure it out - minor annoyance.

What is the proper format for a phone number to enable sms messaging? I can't seem to get it to work. have tried area code phone number (no dashes), 1 area code phone number (no dashes), and also added the country code. +1 area code phone number (no dashes) so:

614xxxxxxx
1614xxxxxxx
+1614xxxxxxx

None of those worked. It looks to be a free-form field, so instead of trying the numerous versions of phone number display paradigms I know, I thought I would ask here.

You may want to consider putting a examples of the correct format of phone numbers under or next to the box in small light grey text. The variations among regions of the US and among different countries is astounding.

thanks