Phone and Internet customers are known to stick with older plans in order to lock in a monthly price or keep other perks. But at AT&T, that practice will start to come at a cost.

This week, the phone and broadband company said it would raise monthly fees for some of its wireless and Internet customers who are sticking with older plans.

Wireless customers on some Unlimited and Mobile Share plans will see their monthly bills go up by as much as $6 a month for a single line or $12 a month for family plans.

A company spokesperson said AT&T hopes affected customers will consider switching to newer plans, which “offer many additional features, more flexibility for each line on their account and, in many cases, a lower monthly cost.”

It was difficult to determine whether all customers will benefit from switching from an older plan to a newer one because AT&T said it will not publish a list of the plans that will be affected by its price increase. Instead, AT&T said the company will notify customers by e-mail and through their bills.

Broadband customers on older plans could also see their bills increase by as much as $3 a month, the website Fierce Telecom reported on Tuesday. The service, known as AT&T Internet, offers a limited amount of fiber connection with speeds varying from 25 megabits per second (Mbps) to 100 Mbps.

AT&T Internet is different from AT&T Fiber, the company’s next-generation, fully-fiber broadband service. Customers of AT&T Fiber are not impacted by the fee increase. AT&T DSL customers saw a $2 a month fee increase in January, Fierce Telecom said.

AT&T said the price increases were needed in order to cover rising costs associated with the services.