Need help with Satnav

That sounds right. Sat Nav was an option then. It is actually just an SD card that slips into the MMI. You can still get it done now. You need to buy the SD card and get it activated by a dealership.
Lots of threads about it on here.

"No Data" prob means there is no SD Card installed. If it says this then I would assume the Sat Nav feature has actually been activated, therefore it has Sat Nav but someone took the maps out of it. My A3 for example has never had the Sat Nav activated therefore it states "GPS Not Enabled" which is different to what you are seeing. All A3's had GPS/ Sat Nav but it is activated or not at time of buying, depending if the original buyer ticked the option or not.

There are a few steps to get the sat nav working in an A3 with SD Card maps. Yours seems to have the activation done ie, Sat Nav enabled, but now you need to buy maps and then have the maps activated/linked to your car. Audi only job and prob around £250-300. The price they quoted of £600 is usually for the actual activation of the Sat Nav feature + the Maps and pairing to your car.

Loads of info on this site. Search bar will be give you various results. This is a VERY confusing topic and it seems your salesman is confused. I would contact Audi directly or pop in as they will know your cars spec. Alternatively log on to myaudi.com and see your cars spec. Should be on there I think.

Mine says "Please insert data media" - it's booked in for an upgrade to the latest maps (2018) in Audi Cambridge for £247 inc VAT and labour. They've said it's basically a new activation (they need to connect the car to Audi Germany for activation with the new card/upgrade) and the previous owner didn't leave the SD card.

Be very careful where you go though, Audi Hull quoted me £390 and said that's the lowest they could possibly go (as it was base cost for them) until I showed them the quote from Cambridge Audi, they then price matched it.

Also, my SatNav has said that it's not enabled a few times too, but a reboot of the system returns it to the please insert media state - so watch out for that when speaking to Audi as they may say it needs enabling (and you may incur further charges).

Another edit... I also bought a Phone Holder (link to follow) which is actually really sturdy and well built! https://www.amazon.co. uk/BenchMart-Holders-Gravity-Linkage-Samsung/dp/B07BRR638H/ref=sr_1_1_sspa?ie=UTF8&qid=1527065499&sr=8-1-spons