HOUSTON -- New ZIP codes in three Houston-area communities are causing headaches for some residents, KPRC Local 2 reported Tuesday.

The U.S. Postal Service said that due to population growth, three ZIP codes in the Houston area have changed. Those cities include Baytown, Richmond and Sugar Land.

Some residents said the change that took affect on July 1 has brought a lot of trouble. One woman said her bank, insurance and credit card companies do not recognize the new ZIP code.

"It's been a nightmare so far," Sugar Land resident Michelle Robinson said. "What if I got into a horrible accident and went to the ER and they denied care for me or I was left with a big bill?"

A U.S. Postal Service spokesman said residents and business owners should have patience because many of the companies have not updated their software to recognize the new ZIP codes.

"Not all companies do it immediately, so the best way to go is to tell your mailers to go to the USPS.com Web site and to verify the new ZIP code and upgrade their information," said Dave Lewin.

The post office said the changes will help deliver mail more efficiently with the growth in population.

Nationwide, 47 ZIP codes have changed. A total of 40,000 people in the Houston area have been affected by the ZIP code change.