Yes, you can, but, the customer calling you from abroad will be charged international rates for the call. Calls to a toll-free number are paid by the call's receiver, but, when dialing from another country the caller will be charged according to international rates. Calling a toll-free number registered in the U.S. (or any other country using the NANP) is possible, and once the call goes through you will be informed that the call isn't free. Calling a U.S.-registered toll-free number from the U.K., for example, would require you to add the 00 prefixes to the 1-800-XXX-XXXX number. Another way to dial North American toll-free numbers from abroad is to replace the 3-digit toll-three codes with other codes, and a good example would be 880 replacing 800, which would make the U.K. to the U.S. call from above become 1-880-XXX-XXXX.