I am hoping someone has current Medicare information and can help me answer this question. When I first became oxygen dependent I paid a copayment monthly for my stationary and portable concentrators for the first 3 years and was told there would be no charge for years 4 and 5. I am now in year 5 and suddenly my provider is billing me again for a 20% copayment. I've talked to the provider and to my insurance and both tell me this is the current practice, and both claim no knowledge of a 5 year agreement with Medicare. Anyone here have any similar experience?