Military OneSource does confirm the number on their website. The lady I spoke with was not aware of the overseas number, but I did find this in their FAQ section.
Q: How do I find out more?
A: Call Military OneSource at 1-800-342-9647 (CONUS), or 800-3429-6477 or 484-530-5908 (OCONUS). For more information on calling Military OneSource from overseas visit www.militaryonesource.com
and click on “Contact Us.” A consultant can give you more information about online consultations and discuss your options with you.