The Federal Telecommunications Institute of Mexico implemented a new standard for 10-digit dialing effective August 3, 2020. 

Under this new plan, all phone numbers must be dialed using a 10-digit format. The "01" prefix, which was previously used for long-distance, 800, and 900 numbers, is now unnecessary. This means that you can dial long-distance numbers starting with "00," and when dialing a country code for Mexico, use "52" followed by the 10-digit phone number.

Additionally, the prefixes 044 and 045 are no longer required when dialing mobile numbers.

For more information on these changes and their implications, please visit the relevant resources.