You would have to be more specific. Are you using a SIM card you purchased in Mexico? Are you using your Verizon SIM card? If you are using the Verizon SIM card, had you previously approved international calls on that line? If not, international calls would not be allowed. I believe the default is that they are blocked, but can't remember since I performed this task so many years ago. I have 4 lines and 3 of those lines have international calls blocked on them, meaning 3 of those phones would not be usable in Mexico with the Verizon SIM card.