While iPhone users seem to spend a lot more money in general, they still have the last laugh when it comes to wireless bills — on average, Windows Mobile users pay the most for their wireless services and iPhone users pay the least, according to a recent study by Pageonce.

The study found that Windows Mobile users typically spend around $205 every month on their wireless bills, followed by Android users paying $197 and BlackBerry users paying $194. iPhone users came in at the end of the pack, paying only $165 each month for their wireless service.

Meanwhile, iPhone users are on a much bigger spending spree. The study found iPhone users spend 35 percent more than the rest of smartphone users, based on how big their credit card bills were. iPhone users racked up around $6,900 in monthly credit card bills, while the next highest smartphone batch (BlackBerry users) only paid $5,700 in monthly credit card bills.

Most iPhone users are older. more wealthy, and have a little more free cash, which could explain the larger credit card bill, according to a report by Nielson. It’s no surprise that BlackBerry comes in at least second place, as a large portion of its customers are enterprise users. A large chunk of that could easily be chalked up to corporate expenses.

The monthly bill could be attributed to AT&T’s payment plans, which recently dropped a touch with the introduction of its tiered data plans. The new plans only charge $15 every month for 200MB of data usage and $25 per month for 2GB of data usage, compared to the old $30-per-month all-you-can-eat plan. The new plan makes users pay an extra $10 for each additional gig of data they consume. AT&T claimed that nearly 98 percent of its smartphone users used less than 2 gigabytes of data each month.

The study looked at 275,000 random smartphone accounts between the beginning of October and November. It’s highly likely that those numbers will grow over time, as the number of people buying smartphones grew from 16 percent to 23 percent of all phone carriers between 2009 and 2010, according to a report by Nielson. Another thing to consider is the introduction of the mythical Verizon iPhone, supposedly arriving early next year — and Verizon’s commitment to an unlimited data plan.

It’s also worth noting that the study focused on older Windows Mobile phones. The wireless service numbers for new Windows Phone 7 users could potentially look very different.