search for: coumbia

I've had this discussion in the office and with some vendors, but no one has a solid answer, hopefully someone here does. What is the proper way to format a caller-ID here in the U.S.? Is it: +15705551212 or is it +5705551212 I've always seen it +15705551212, but as I understand it the country code for the US is 011, which to me would indicate you put 011-570-555-1212 as the callback