Enlarge (credit: Getty Images | Ronald Martinez)

AT&T is imposing $10 and $20 monthly price hikes on users of older unlimited wireless plans starting in August 2024, the company announced. The single-line price of these 10 "retired" plans will increase by $10 per month, while customers with multiple lines on a plan will be hit with a total monthly increase of $20.

"If you have a single line of service on your plan, your monthly plan charge will increase by $10. If you have multiple lines on your plan, your monthly plan charge will increase by a total of $20. This is the total monthly increase, not per line increase," AT&T said.

AT&T has offered a dizzying array of "unlimited" data plans over the years, all with different limits and perks. While unlimited plans let customers avoid overage fees, speeds can be slowed once customers hit their high-speed data limit. There are also limits on the usage of hotspot data.