(David Paul Morris/Bloomberg News)

The nation's biggest wireless carriers are making it a bit harder to keep your grandfathered unlimited data plan.

AT&T intends to raise the price of its “legacy” plan, which it no longer sells, by $5 a month in March — bringing the total monthly price of the plan to $40. This marks the second time that AT&T has upped its rate for this group in 12 months.

Verizon, meanwhile, has a new policy whereby any customer on a grandfathered unlimited plan who consumes more than 200 GB of data in a month must switch to a metered plan or be disconnected by Feb. 16. Customers won't be able to get around the cut simply by reducing their usage now and ramping it up later; in a statement to The Washington Post, Verizon said it will “review data usage regularly” moving forward.

The two moves, which were reported previously by DSL Reports and Ars Technica, make grandfathered plans less attractive to the small group of subscribers who have them. For years, carriers have been pushing customers to abandon unlimited plans and shift to plans with data caps and overage charges, which allow carriers to make more money. Executives have previously called unlimited plans a money-losing proposition; on Wednesday, AT&T said in a statement that customers get "several benefits" from its newer plans that aren't provided by its "legacy unlimited plan."

While grandfathered unlimited plans appear to be under sustained assault, that doesn't necessarily mean the unlimited plan is dead. AT&T recently reintroduced a version of its unlimited plan, hoping to lure customers with the promise of all-you-can-eat data. But it comes with a catch: To get it, you also must subscribe to one of AT&T's two TV services, DirecTV or U-verse.

T-Mobile, meanwhile, has doubled down on unlimited, encouraging new and current subscribers to switch to its T-Mobile One plan. But some customers have complained that, at $70 for the first line (and $85 if you want your mobile videos in HD), T-Mobile One is more expensive than their existing plans.

The more recent unlimited plans from T-Mobile and AT&T operate on a “different logic” than the older, grandfathered plans, said Paul Gallant, a telecom analyst at Cowen & Co.

“T-Mobile did some re-pricing and is gambling that … volume makes up for additional network costs,” he said. “AT&T’s logic is [that] unlimited makes sense when paired with the economics of pay-TV service.”

The current interpretation of “unlimited,” in other words, still comes with trade-offs. The calculation for consumers is whether their old unlimited plan is still a better deal.