T-Mobile customers holding on to their legacy plans can expect to see higher bills come June.

"For the first time in nearly a decade, in response to rising costs and inflation, we’re making small adjustments to some of our oldest rate plan prices," explained the T-Mobile website. "Beginning June 5, the rate of your voice plan will increase by $5.00/line per month."

T-Mobile declined to specify what specific plans are included in the pricing change.

The website claimed that the provider still offers the "best value in wireless" even with the adjustments, saying its customers save "an average of approximately 20%" versus some competitors, for comparable services.

Customers were advised that services, benefits and promotional pricing will remain the same and the additional charges will automatically be added to bills after June 15.

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"T-Mobile is committed to offering the best value in postpaid wireless with low prices and a differentiated, best-in-class 5G network – and we have no intention of ever changing that," T-Mobile said in a statement to USA TODAY on Thursday. "The majority of our customers are not included but the fraction who are heard from us yesterday."

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What T-Mobile plans are impacted by a price hike?

The price hike applies to older plans, though T-Mobile has declined to confirm which are impacted. Customers have largely pieced the information together by comparing notes online, reporting what plans they have and what dollar amount increases they were told to expect.

As compiled by The Mobile Report, not all customers are reporting $5 increases. Some said their notifications told them to expect a $2 increase, depending on the plan.

Users have reported increases for the following:

• T-Mobile ONE plans
• Simple Choice plans
• Magenta, Magenta Max, Magenta 55 Plus and Magenta Amplified plans

As reported by CNET and The Mobile Report, an internal memo sent to employees specified that more recent Go5G plans will not see price increases, nor will any customers who have the T-Mobile Price Lock guarantee or free lines, reported CNET.

Users with other account types have likewise said they were informed of a planned price increase, including business account holders, as well as smartwatch and Beyond the Smartphone (BTS) lines used for other smart devices such as tablets and hotspots.

Last year, T-Mobile received backlash for plans to migrate users with older services over to more expensive, newer ones. Multiple outlets reported that customers with One, Simple Choice and Magenta/Magenta 55 Plus plans would be moved over to newer versions, an initiative that was quickly squashed after its details were leaked.

T-Mobile CEO Mike Sievert later said it was meant to be a small-scale test, not "a broad national thing," but the company decided against running even a limited test after overwhelmingly negative customer feedback.