What's medicare supplement insurance? Medicare supplement insurance can help pay some of the health care costs that original medicare doesn't cover. The medicare enroller will help you find the most affordable plan quickly. We have agents standing by every day that will help match you to the right plan to fit your needs. Keep in mind that medicare supplement plans can only be used to pay for original medicare expenses; these plans can't be used to pay for costs you may have in medicare part c. If you enroll in a medicare advantage plan, you can keep your medigap plan as long as you keep paying the monthly premium, but you won't be able to use your medigap benefits to pay for your medicare advantage plan costs.