To call a US toll free number from Mexico, dial as follows: 800 numbers Dial 001-880-then the number 866 numbers Dial 001-883-then the number 877 numbers Dial 001-882-then the number 888 numbers Dial 001-881-then the number.o call a US toll free number from Mexico, dial as follows: 800 numbers Dial 001-880-then the number 866 numbers Dial 001-883-then the number 877 numbers Dial 001-882-then the number 888 numbers Dial 001-881-then the number.