T-Mobile has announced a new $40 Simple Starter plan that promises unlimited talk, text and 500MB of high-speed data. The key selling point of the new plan, which targets the low end of the wireless service market, is that there are no overage charges because, well, there'll be no data overages.

Whenever you bump up against the 500MB data cap, you'll be prompted to either buy a day or a weekly pass, or sign up for one of the carrier's Simple Choice plans.

All the major carriers have been targeting budget customers over the past few months. Verizon recently announced a More Everything plan that provides more data, 25GB cloud storage, and unlimited international messaging.

With the new plan, T-Mobile is not only trying to retain its existing customers, but also hoping to attract new ones. The company has said that it will also pay the early termination fee of those who are coming from other carriers. The plan, which goes live on Saturday, also qualifies for zero down interest-free financing, and the carrier's Jump upgrade program.

The Simple Starter plan, however, has a few limitations. For example, it can't be bundled with a family plan, and it doesn't provide extra features like global roaming or international texting.

T-Mobile CEO John Legere said that the company has more to reveal over the next two days, so stay tuned.