Effective May 20th, T-Mobile is making some sweeping changes to their current billing methods for new postpaid customers. Customers are now billed in arrears, meaning you pay for usage after you’ve actually used it. Now, effective May 20th, new customers signing up on the T-Mobile network will be billed in advance for reoccurring charges.

This change will only affect new customers to T-Mobile — there doesn’t seem to be any indication existing customers will be moved to “Bill Current.” Upon new activation, new customers are assigned to the next possible bill cycle end date. Usually the bill cycle date will fall without four days of the activation date of service.

This isn’t a surprising change, considering most of the nations wireless carriers have billed in advance for some time. In all honesty, I’m actually surprised T-Mobile has waited this long to make the change. For the first month of service there can be a bit of sticker shock, but overall, you don’t spend any more money than you would in arrears.

There’s a bunch of details below, but for the most part this is exactly what those of you who have spent time on other wireless carriers have come to expect. First bills include a prorated charges, the full monthly recurring charge and the activation fee.

No word on what happens to existing customers upon changing rate plans.