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.