If you're still clinging to your Verizon unlimited cell phone plan, your monthly bill is about to jump by $20.

Verizon (VZ) is planning to raise the price of unlimited data plans from $29.99 to $49.99 per month. The company confirmed the move to CNNMoney on Thursday morning.

It's yet another sign the company's trying to force people to let go of their highly prized plans that remain only because they were grandfathered in.

The unlimited data is only part of a cell phone bill. Talking and texting are extra. Right now if you're on Verizon's 450 plan, that costs $59.99 per month. Add the new higher rate for unlimited data, the total monthly cost will look more like $109.99, plus fees.

Verizon customers will see the increase starting on monthly bills that arrive on Nov. 15 or later.

Phones now gobble data as they stream social media, videos, music. In recent years, smart and frugal people have resisted upgrading to limited data plans. Any data cap is easily surpassed, and extra expensive fees kick in.

That's why major carriers have done away with unlimited data. It hogs their network. Instituting limits lets them better manage the network's bandwidth.

Verizon has already exerted some force on this band of unlimited data resistance fighters. It stopped offering unlimited data plans in 2011, so it wouldn't renew two-year contracts. These people continued on Verizon on a month-to-month basis, and they also had to pay full price for new phones.

With this more expensive plan, unlimited Verizon customers will once again be allowed to buy new phones at an upfront discount that customers pay over time.

AT&T (T) is similarly aggressively trying to coax people off unlimited plans. Try to upgrade to a new iPhone a month before your two-year contract is up, and AT&T will say no way -- but it would gladly let you upgrade now if you just get off your grandfathered unlimited data plan.

But Verizon is the first to push off the last remaining stragglers by raising the rent. The company said it only applies to less than 1% of its customers.

Verizon spokesman Chuck Hamby said the company will take the extra revenue to reinvest in strengthening its cell phone network -- widely regarded as the move reliable in the United States.

He justified the price increase, saying: "You're getting access to the Verizon network, and that's where the real value lies."

This is the kind of thing that smaller competitors like T-Mobile will jump on and criticize. T-Mobile's unlimited plan costs $80 per month. But keep in mind that customers still complain about the quality of cell phone connections on other networks.

"How do you put a cost on reliability?" Hamby said. "If you charge a little more, but you're providing an excellent service, customers don't mind that. They know you get what you pay for."