The war among wireless providers continues to intensify. AT&T is going after T-Mobile customers, with a new promotion.

If a T-Mobile customer switches to AT&T, AT&T says it will give that customer a $200 credit, and up to $250 more for trading in his smart phone. 

“I think the first thing that hit me was this: AT&T declares war on T-Mobile,” says Ramon Llamas, research manager for IDC’s mobile phones team. To be fair, fighting may have escalated. The two carriers have been going at it for a while now.

According to Llamas, “the proof is going to be in the pudding.”

“When people are going to see how much money I am going to save, and how much I am going to end up spending,” he says.

A T-Mobile customer who switches to AT&T could face a penalty for breaking his contract, if he has one, and on top of that, there is the cost of the smart phone. Customers usually pay for that over the life of a contract.

That $450 credit “might not be nearly as much as you think,” says Weston Henderek, principal analyst with Current Analysis.

He says AT&T used to have a leg up on T-Mobile, but today “the differences are much smaller than they’ve been in the past.”

AT&T has had trouble selling customers on higher-end plans, and Henderek says throwing money at them just might help.