I had a similar experience today.  I went to Praktiker to change an incompatible bulb.  I got the "no English and walk away" attitude.  Then, my American instinct kicked in, and I was determined to go through with it.  So I went around the whole store until I found someone who spoke English. Luckily it was a very nice guy who ended up taking me through all the nasty cashiers in order to get the exchange.  Ha!