Ian,Ribeye.
It is 39 TL to top up the 4 gb which is valid for one month.
When you go on line the VINN (page) will show you what to have left and to what date. I find if I try downloading a movie or wathing TV shows I can use my 4 gb within a week. This makes it a very expensive alternative.
However I do all the web beousing on the dongle at home and when we are out and about with free wyfy, to down load movies then.
I actually paid around 150 for my first month with the dogle. (Every time you top up a new month starts)
Hope this helps