We recently contacted RESMED requesting information . We called RESMED several times with our unit's serial number just trying to obtain some basic information such as local authorized service locations. We own our Activox concentrator unit and wanted to be able to have the sieve columns replaced which we are told is required about every 12 months. Also using our units serial number we were interested in obtaining the service history of our Activox Lifechoice portable oxygen concentrator. They RESMED customer service is a joke. The first time we called the young woman who answered was pretty much clueless and could not not answer basic questions.The second time we called RESMED,which was a few days later, a different RESMED customer service rep answered the phone,she was rude and hung up on us. RESMED seems not to care about helping seniors who can't purchase a $2400 new unit. It appears RESMEDS business model is concerned mainly with large account medical equipment companies and/or their rental equipment that has a guaranteed Medicare payment. On the phone RESMED claimed that they don't have or don't keep any service records for their units, yeah right! We contacted our local RESMED authorized service center with the info RESMED gave us and we were informed they won't help us because they only service RESMED units that they rent to patients. Using the internet we are able to find a few out of state RESMED service centers. What a delight it is to find out that the lowest price we can find to have our unit's 2 sieve columns replaced was around $430 which breaks down to ($175 parts + $175 labor + $40 to send unit in + $40 return shipping). Most likely the service center would find additional services required increasing the annual cost to at least $500 each year for a 2 year old unit with only 100 hours of use on it. Overall maybe purchasing a used an Inogen might be the way to go. On the phone the Inogen customer service people are at least friendly.