Hello @charley, can he/she try to dial the exit code 011 and dial 52 plus the rest of the numbers. Thank you!
011 52 is the code to call from US to Mexico, she just tried anyway but it didn’t work, still get the same “wrong number”’ message. When you want to call to Mexico from US you need to dial 011 52 + the number, so it’s not related at all to Mx 1-800 numbers. She is trying to call from within Mexico to a Mexican toll-free number.
This might need to enable the international call for Mexico. Click HERE for more information.