If you are on Medicare, you only have three weeks left to pick out a plan for coverage in 2019.

But how do you know which plan is best, and how do you avoid the Medicare scams that are targeting seniors right now.

Commercials are in full swing selling Medicare Advantage coverage plans, but how do you know what's legitimate or a scam? We turned to Raymond Hurd, a Regional Administrator for the Centers for Medicare and Medicaid Services. He warned about any phone calls or personal visits.

"We're never going to call you, so if somebody calls and says they represent Medicare, it's probably a fraud. If they're trying to tell you that you can get something for free, that Medicare's going to pay for, it's probably a fraud," said Hurd.

About two-thirds of Medicare recipients get benefits through government-run original Medicare. The other third enrolls in Medicare Advantage plans. But with Advantage plans you must make sure your doctors are in-network for maximum reimbursement. And just like private health insurance companies, there are different Medicare Advantage plans.

"Some Medicare Advantage plans may cover hearing or vision and others may not. Their monthly premiums may vary too, so you need to sort of shop around and see what best fits your needs," he said.

Hurd says it's best to go to medicare.gov online to compare plans that are best for your needs or call 1-800-medicare, where a rep will explain each plan or refer you to a local counselor.

"I get feel good stories every year from counselors, from people that save hundreds of dollars because they switched to a different plan," said Hurd.

Every year Advantage plans change in cost, coverage and providers and it's projected that the average basic monthly premium for a Part D prescription drug plan is going to be the lowest in several years. So we can verify to avoid fraud, it's best that you initiate your research on a legitimate government site.

Enrollment ends on December 7.