The Greek economy (pt II)

Given the extremely unconvincing quality of this forgery, you would be forgiven for thinking that what follows is a series of Conway-style 'Alternative Facts'. In fact, what I am about to tell you is the real 21st Century Truth.

In Greece, in the 21st Century the fax machine is still a very popular means of business communication 
When phoning a Greek company the line is still very likely to cut into fax and not an answering service.

In Greece, in the 21st Century it is still possible to pay Cash on Delivery for mail order items
If you wish to order something and have it delivered to you at home you pay the cost of the item, the cost of the shipping, plus 3€ for CoD. In theory it would therefore be possible to bankrupt a company by continually ordering things CoD and failing to pay for them when they arrive.

Since July 2015 holders of Greek bank accounts have not been permitted to withdraw more than 60€ per day in cash
From the outset this translated to 420€ per week, though that was not initially made abundantly clear and so long queues developed at ATMs while every family member withdrew their allocated 60€ every day. Recently this has been extended to 840€ per fortnight but the cash limit remains in place.

We received a call from a courier today telling us he had a delivery and where could he find us. I explained that we are 5km outside the village and would come in to collect, where would I find him please? In front of the school.

I dashed in, he wasn't there, I asked at the kiosk, he hadn't been seen, so where was he? We called, he had been delayed, he'd be with me in five minutes. When he arrived he apologised for the delay. Somebody had tried to pay him for a delivery using a 500€ note. Nobody had change.
Obviously.

Who would have such a note and why would they think it was exchangeable for anything? Is it even legal tender?