Everyone might be happy to hear that all the large cell phone companies are lower the prices of their unlimited voice plans to about $60 a month but that is not what you need to worry about. Although your voice plan might be going down, cell phone providers are secretly higher your data plans.

It began with Verizon Wireless. Last month, that company began requiring certain non-smartphone customers to subscribe to a data plan that costs at least $10 per month. Verizon’s move marks the first step in a larger trend to make up for carriers’ lost revenue from voice.

Accordingly to CNN, Smartphone owners are used to paying for an unlimited data plan with T-Mobile, Verizon and AT&T customers doling out the most: roughly $30 per month. Sprint offers a slightly different service, but also requires smartphone users to subscribe to an unlimited plan.

But non-smartphone customers aren’t used to high-priced data plans. Less expensive, limited data plans have been largely available but not widely adopted. Verizon said it began to require new customers who purchase so-called “3G multimedia” phones to subscribe to a data plan in part so that they could get the full functionality out of their phones.

Previously, Verizon offered non-smartphone customers two data plans: $10 for up to 25 megabytes or $20 for up to 75 megabytes. In January, Verizon eliminated the $20 plan and replaced it with a $30 unlimited plan that was previously available only to smartphone users.

3G multimedia phones include a wide array of phones, ranging from the LG enV Touch, which has a touch screen and a QWERTY keyboard, to the Motorola Entice, essentially a standard flip phone that can access the mobile Web.

Other carrier will follow suit. So watch your cell phone bills carefully because those data plan cost could bit you in the rear end.