So, Avea texted me when I was at Trabzon for a family visit and a quick seminar about free software as a sidekick. Very early in the morning I did a SIM switch and it was on.
About 2 months with Avea, many cities, a lot of travel and on-the-go conference-calls; I'm happy to report that I have experienced not a single glitch. Avea network works as expected. I'm a satisfied customer.
Now that being said, call sound quality is slightly worse than expected. Avea is a GSM1800 network, and it drains my phone battery slightly faster, compared to any GSM800 network (Turkcell, for example).