Probably a slightly different issue, but I responded to an email from Bancomer that I received the day after I replaced my debit card. The email congratulated me on my new card, had my full name, address, and account number, and instructed me to fill out information necessary to verify it for security purposes. The next day, 7000 pesos was taken from my account. When I reported it to the bank, they told me that Bancomer never sends out emails, and I should not have responded to it. They sent a report to the main bank, who started an investigation. This was back in April. Now 4 months later, they still have no answer for me. When I call, they tell me it is still under investigation, and that I should not call them - they will call me.
Many people that I have shared this with have told me they know someone who had a similar experience with losing money from their Bancomer account.
All this is to say use extreme caution with any email from Bancomer, no matter how official it looks. The one I received was extremely offical looking - down to the tiniest print, logos etc. It might be wise to print out any email and take it directly to the bank, rather than fill anything out online.