Seniors and the disabled who are enrolled in some Medicare managed-care plans will get telephone calls from their insurers next year — just to be sure they intended to sign up after all, a Medicare official said Wednesday.

The precaution is a result of confusion and unscrupulous behavior on the part of some insurance agents.

The plans in question are part of Medicare's managed care program, in which the government pays a private insurer a monthly fee for providing enrollees with health care. One type of plan, called "private fee for service," has had skyrocketing enrollment in the past year because of the generous subsidy the government provides as well as fewer restrictions on which health care providers a patient can see.

More than 1 million people have enrolled in private-fee-for-service plans.

A Medicare official acknowledged Wednesday that some of those enrolling were misled or not told everything they needed to know about the plan. So Medicare will require insurers to use clearer language in marketing materials and make a follow-up call to confirm seniors understand the features of the plan and wish to enroll.

"Our experience shows that on occasion, private-fee-for-service plans have not been clear about what they offer our beneficiaries — and what they don't provide," said Abby Block of the Centers for Medicare and Medicaid Services.

State insurance commissioners have been raising concerns about tactics that some agents have used to enroll beneficiaries.

Sean Dilweg, the insurance commissioner in Wisconsin, told the Senate Aging Committee that 37 out of 43 states surveyed have received complaints about misleading or confusing marketing practices. Some just wanted coverage for their medicine but found themselves enrolled in plans that cover all of their health care.

"In the most troubling of these cases, unscrupulous agents have enrolled beneficiaries with dementia into an inappropriate plan," Dilweg said.

Sherry Modwell, a special agent with Georgia's Insurance and Fire Safety Commission, said one insurance agent signed up people for a drug plan, then switched their coverage to a managed care plan without the knowledge of the patients or their guardians. In another case, beneficiaries were enrolled in a managed care plan even though they had never met or talked to the agent who enlisted them.