If you've been on the same T-Mobile plan for years, listen up: Not only will T-Mobile move you into a new plan this month, you may have to pay more as a result.

As reported by CNET (which is owned by Lifehacker parent company Ziff Davis), T-Mobile will end a number of legacy plans, which will cancel "over 1,100 legacy billing codes." The company has started contacting customers on legacy plans to let them know about these changes. It seems T-Mobile has not specified which plans in particular are on the chopping block, but that some run "10 to 15 years" back. As CNET highlights, that could affect "Simple Choice," "T-Mobile One," "One Plus," and "Magenta" plans. In addition, legacy Sprint plans will likely be affected, if users had plans grandfathered over following Sprint and T-Mobile's merger.

In a statement to Android Authority, T-Mobile explains its reasoning behind the changes. These plans are the company's oldest, many of which were designed for the "3G and 4G eras." In addition, customers transitioning to current plans will have access to a five-year price guarantee. T-Mobile won't be shutting the lights all at once. These changes should take place over the coming weeks, and will be reflected by the following billing cycle. If your plan is affected by these changes, you should receive word either by text or through the T-Life app as soon as today.

How much more will customers pay on new T-Mobile plans?

The immediate downside to losing your legacy plan is, of course, losing your previous rate. While there are no guarantees at this time, it does seem like users who T-Mobile moves to a current plan will largely pay more than they did on their previous plan.

The good news is that the new plan may not be that much more expensive. T-Mobile's statement to Android Authority says that some customers' plans won't change at all, while others will see a "modest adjustment." Android Authority says that T-Mobile confirmed that the "average" change customers will see will be $4 per line.

What do T-Mobile customers have to do?

According to T-Mobile, nothing. The company says it will be automatically enrolling legacy plan customers into current plans. In fact, Allan Samson, T-Mobile's chief marketing officer, said that "absolutely nothing is required of the customer, and it just is going to happen."

T-Mobile will supposedly move you to a "comparable" plan, including "Essentials," "Essentials Saver," "Experience More," "Experience Beyond," and "Better Value." While these may come with new features, they may, of course, come with that added price tag. Unfortunately, it doesn't seem you can contest the change, and must wait until T-Mobile takes action before you know what plan you've moved to.

If you're on a legacy plan, my advice is this: either wait and see what T-Mobile picks for you, or contact the company and negotiate. There's no guarantee what it might offer you, but once you know what your choices are, you can decide whether to move to another provider, or take what T-Mobile is offering.