First, what they meant was that the MacAir itself was not eligible for any Apple support as they will no longer support your MacAir model. They did the same thing for my early 2010 MacBook Pro. You don't say what model MacAir you have. Just Google the following; "What MAC OS version can my model MacAir run"? You should be able to run Yosemite..
Assuming you bought the MacAir from a reputable source, they should have wiped the MacAir clean and unregistered it from the Apple servers. When you booted up, the MacAir would have gone straight to the Apple servers and asked for a Apple ID. Assuming it did, log onto the App Store. Click on downloads. That will give you a list of any software bought or free from Apple. If Yosemite is listed, just click on download and the software will download.
If it's not listed, your only other option is to buy a copy. You never say what OS version it is currently running?
hi
Our daughter saved hard for a MacBook Air and unfortunately the guy failed to tell us that it’s just outside the 2012 cut off for upgrade support etc
Does anyone please know if we can download Yosemite or the other one to try and at least get it to 10.9 or 10.10
Thank you
Click on the Apple on the top left and then click on About this MAC. That will tell you all about the MAC including which version software is installed