For the longest time 210 has been the area code that represents San Antonio. Beginning in September of 2017, 10-digit dialing will be required for making outbound calls in the local area. The new area code "726" will be given for new numbers beginning in October of 2017. People that still have the "210" area code will keep their area code.
A cool fact is that the new area code spells out "SAN" for San Antonio.
Get ready for the change.