Just got a call on my phone from a number I didn't recognize. I answered it in Russian.
I threw a few phrases out in Russian while the person (from what scam operation, I don't know) kept asking to speak to me by name. My replies in Russian grew louder until eventually I said Ya nye govreet pa Inglizi! (I don't speak English!) whereupon she hung up.
What fun... 
= new reply since forum marked as read
"Ya nyeh govreet pa Ruskyi! and try a different language... 
Ya nye gavaryoo pa Angleesski (Я не говорю по-английски
Then you'll have Russian grammar on your side (gavareet is 3rd person singular, and the unstressed "o" in Russian is pronounced like an "ah" ). Ingilizce is "English" in Turkish.
These days, if it's a number I don't know, especially if it's a country prefix I don't recognize, I answer with "namasté." Since they are usually Indians calling from some call center in Delhi or Chenmai, or wherever, that usually stops them in their tracks just long enough for me to know I have said the right thing. If THAT doesn't work, I just continue in Catalan or Swedish. Never German or English.
Here in western Europe, the Romanians (both European and Gypsy) have brigades of young girls they have pressed into service to scam people on the street. I pity them, as they often come from families back home that see this as the only way to get out of debts they have run up to crime clans. The girls have gone to school enough to learn passable English. It's the crime clans I hate, not these poor girls themselves, but I have neither the time nor the inclination to help out this nasty exploitation. The EU claims to be against the practice, but the clans shoot back, so they usually do what EU bureaucrats do best, which is nothing. My tactics when approached by these girls is similar to yours. My knowledge of English plus the local language (wherever I am) has taken a spontaneous vacation to the Caribbean, and all I can remember is Russian or Swedish. I once made the mistake of saying "nu vorbesc angleza," which is Romanian for "I don't speak English." I got followed for the next 500 meters being harassed as to why I should help out a fellow Romanian. I never made THAT mistake again!
I appreciate it. 
