I applied online, explicitly mentioning that my experience was with Java rather than C#
I had a first interview in September, which consisted of some CV questions, the interviewer filling out a form about my experience, and a written pen and paper test. This pen and paper test was based around C# instead of Java
About a month later I got invited back to a second interview. This one repeeated the CV questions and form filling, but the technical exercise was different. It involved fixing some bugs, fixing some tests, and writing some new code. This was also in C#. The interviewer asked why I was taking a C# interview even though I don't have experience in it?!