Data hogs who are considering purchasing a smartphone or tablet with an AT&T plan may want to act quickly, or find the nearest wireless spots. AT&T is raising the price of its wireless data plans and changing the data limits for new customers starting Sunday. The changes could add up to an extra $60 a year.

AT&T announced that new smartphone customers would have a choice of three new monthly data plans: $20 for 300 megabytes,or  $30 for 3 gigabytes. For $50, smartphone customers get 5 GB of data for tethering, or for sharing the Internet connection of another mobile device.

While the company described the new plans as a "great value," Mike Gikas, Consumer Reports' electronics senior editor, said, "giving you more data that you're probably not going to use and charging you more is just a price hike."

New smartphone customers who want additional data will have to  pay $10 per additional gigabyte on the 3 GB and 5 GB plans. New customers with the 300 MB plan can get an extra 300 MB for $20.

Because data usage over Wi-Fi does not count against a customer's monthly data usage, AT&T said it encouraged customers to keep their device's Wi-Fi turned on. However, smartphone users who enable Wi-Fi on their phone may burn through  battery power.

Existing smartphone and tablet customers can choose to keep their current plans, which are $15 for 200 MB, $25 for 2GB and $45 for 4 GB, and also include  tethering, according to Consumer Reports.

Under the old $25 plan, AT&T charged an overage fee of $10 per GB, so the new $30 plan could save data hogs $5 per month, according to Time.

The new tablet plans are $30 for 3 GB and $50 for 5 GB.

"Customers are using more data than ever before," David Christopher, the chief marketing officer at AT&T Mobility and Consumer Markets, said in a statement. "Our new plans are driven by this increasing demand in a highly competitive environment, and continue to deliver a great value to customers, especially as we continue our 4G LTE deployment."

Most people do not come close to using 2 GB of data unless they  constantly stream media, for example, by watching movies on their phones through Netflix or iTunes.  When AT&T introduced its tiered pricing system in June 2010, it said that 2 GB satisfied 97 percent of its customers, Gizmodo reported.

"The magic number is usually 1 GB, which is probably why  most people went for the 2 GB plan," Gikas said.

Those with unlimited data plans might still feel stifled if they'd been downloading and streaming an extremely large amount of data.  AT&T announced in July that the top 5 percent of data users experienced slower speeds starting this past October.

In July, competitor Verizon Wireless eliminated unlimited data plans for new smartphone customers and introduced plans of $30 for 2 GB, $50 for 5 GB or $80 for 10 gigabytes of monthly data usage. Verizon customers are charged $10 more for each additional GB.

While AT&T, Verizon, and T-Mobile have introduced tiered pricing for data plans,  Sprint Nextel Corp., the country's third-largest carrier, is the only one  to still offer unlimited plans.