Olly Richards from IWillTeachYouALanguage.com wrote an interesting blog post about the problem of people answering back in English instead of the language you are learning.
So you want to practise a language but they answer back in English. What do you do?
Here is a short summary:
Strategy 1: Pretend you don’t speak English or pretend you speak it poorly.
Strategy 2: Explain to the person that you want to practise their language and ask them not to speak English.
Strategy 3: Go to a place where they don’t speak English, such as in rural areas.
Click here to read the complete post from Olly Richards.